WO2013041947A1

WO2013041947A1 - Radio communication devices and methods for controlling a radio communication device

Info

Publication number: WO2013041947A1
Application number: PCT/IB2012/001843
Authority: WO
Inventors: Jaya Shankar Pathmasuntharam; Haiguang Wang; Anh Tuan Hoang; Chee Ming Joseph TEO; Wai Leong YEOW; Shoukang ZHANG
Original assignee: Agency For Science, Technology And Research
Priority date: 2011-09-19
Filing date: 2012-09-19
Publication date: 2013-03-28

Abstract

According to various embodiments, a radio communication device may be provided. The radio communication device may include: a data sender configured to send, using a first transmission mode, data to another radio communication device; and an indication sender configured to send, using a second transmission mode, to the other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent from the other radio communication device and an indication indicating that the radio communication device is ready for receiving data. The second transmission mode may include or may be a transmission mode of higher transmission robustness than the first transmission.

Description

RADIO COMMUNICATION DEVICES AND METHODS FOR CONTROLLING A RADIO COMMUNICATION DEVICE

Cross-reference to Related Applications

[0001] The present application claims the benefit of the Singapore patent application No. 201106746-9 filed on 19 September 201 1, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

[0002] Embodiments relate generally to radio communication devices and methods for controlling a radio communication device.

Background

[0003] The mobile data industry is evolving rapidly, resulting in exponential growth in demand for bandwidth. Service providers have foreseen an increasing data growth over the next few years. The growth in mobile data usage is being fuelled by growing 3G penetration, popularity of smartphones and USB dongles, advanced mobile applications and flat-rate data plans. As a result, service providers are facing congested networks which are impacting their service delivery levels.

[0004] Many service providers are beginning to adopt a range of strategies, such as optimization of 3G networks using intelligent policy control, mobile data traffic offload, and transformation to 4G to reduce costs and alleviate congestion. [0005] Mobile data offload, in particular 3 G- WiFi offload, is becoming more and more popular these days. Offload is the ability to move mobile, data traffic from one network to another in a way that is transparent to the subscriber, which is a key component of an effective network congestion reduction strategy. Mobile data offload will reduce costs and improve economies of scale by balancing traffic requirements across networks. The cost savings are significant. Service providers deploying a multiaccess offload strategy can expect savings in the range of 20 to 25 per cent per annum.

[0006] Mobile data offload from 3G to WiFi presents a number of challenges to service providers. First, service providers must ensure that subscribers receive a consistent and comparable user experience regardless of access network, wherein service portability and continuity across multiple access networks is essential. Second, transparent sign-on is preferred, in which a single sign-on process is required to ensure seamless usage of various networks. Third, authentication access in non-3 GPP networks, such as WiFi may not be easy when subscriber authentication data resides in the Home Location Register (HLR) in 3GPP networks. Fourth, smartphone users do not always have WiFi turned on due to the heavy battery drain on their handsets and network systems cannot force a device to switch on WiFi, which present challenges for service providers who want to offload traffic to WiFi. Fifth, the handset's connection manager requires knowledge of WiFi hotspot locations, in particular those in the vicinity of high- traffic cell sites that typically experience congestion. An offload solution also needs to be subscriber-aware, including subscriber location as it relates to available hotspots. Sixth, Simultaneous operation of WiFi and 3G is required, but not all handset manufacturers allow both 3G and WiFi to operate at the same time. In some cases, this can work but under a restricted condition where the WiFi acts as an Access Point (AP). Seventh, WiFi range is short, mainly due to the power of the WiFi transceiver on the handset. In most cases the link would be highly asymmetric, wherein the transmission from the access point would be able to reach the handset but the transmission from the handset is unable to reach the AP. This restricts the offload to happen when the user is static or very near to an AP. Eighth, there might be limited access to WiFi network. In most cases, there will be many WiFi networks in the vicinity of the user but it would be difficult to capitalize on these WiFi APs to provide 3G offload due to the lack of permission and necessary software to enable the switching.

[0007] In practice, allowable transmission power levels of WiFi usually vary from region to region. For example, according to FCC rules, 4W EIRP for isotropic PMP mode is allowed for US. EIRP levels of 20dBm are allowed in the EU. Based on these power levels, the range of a WiFi access point operating in the point to multipoint mode can reach a distance of about 1km. This would make it feasible for mobile network operators to install their own specialized WiFi APs. Long range WiFi nodes can be installed sparsely in the exterior of buildings. With the long range WiFi, the service provider need not depend on the public WiFi APs, which is a nightmare when it comes to controlling quality of service, billing, installation and access management. Long range WiFi would therefore reduce cost and provide larger coverage foot print.

[0008] However, power levels in typical mobile client device, such as smartphones, are usually very low, which usually allow radio ranges of up to about 50m in the uplink. In that case, for example, data from the mobile client may not be able to reach the AP when the distance between the mobile client and the AP exceeds the uplink radio range. The disparity in the radio ranges for the uplink and downlink transmission to the mobile client remains a problem.

Summary

[0009] According to various embodiments, a radio communication device may be provided. The radio communication device may include: a receiver configured to receive data from another radio communication device using a first radio communication channel; an indication generation circuit configured to generate an indication indicating a reception property of the data received from the other radio communication device; and a sender configured to send the indication to the other radio communication device using a second radio communication channel. At least one of the first radio communication channel and the second radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network and a metropolitan area system radio communication network.

[0010] According to various embodiments, a method for controlling a radio communication device may be provided. The method may include: receiving data from another radio communication device using a first radio communication channel;

generating an indication indicating a reception property of the data received from the other radio communication device; and sending the indication to the other radio communication device using a second radio communication channel. At least one of the first radio communication channel and the second radio communication channel may include or may be a radio communication channel according to an wireless local area network radio communication. [0011] According to various embodiments, a radio communication device may be provided. The radio communication device may include: a data sender configured to send, using a first transmission mode, data to another radio communication device; and an indication sender configured to send, using a second transmission mode, to the other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent from the other radio communication device and an. indication indicating that the radio communication device is ready for receiving data. The second transmission mode may include or may be a transmission mode of higher transmission robustness than the first transmission mode.

[0012] According to various embodiments, a method for controlling a radio communication device may be provided. The method may include: sending, using a first transmission mode, data to another radio communication device; and sending, using a second transmission mode, to the other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent from the other radio communication device and an indication indicating that the radio communication device is ready for receiving data. The second transmission mode may include or may be a transmission mode of higher transmission robustness than the first transmission mode.

[0013] According to various embodiments, a radio communication device may be provided. The radio communication device may include: a receiver configured to receive from a first other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent from a second other radio communication device and an indication indicating that the first other radio communication device is ready for receiving data; and a sender configured to send the received indication to the second other radio communication device.

[0014] According to various embodiments, a method for controlling a radio communication device may be provided. The method may include: receiving from a first other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent from a second other radio communication device and an indication indicating that the first other radio communication device is ready for receiving data; and sending the received indication to the second other radio communication device.

[0015] According to various embodiments, a radio communication device may be provided. The radio communication device may include: a data sender configured to send data to another radio communication device; and a receiver configured to receive from the other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent by the data sender and an indication indicating that the other radio communication device is ready for receiving data. The data sender may be configured to send data to the other radio communication device if the receiver does not receive the indication.

[0016] According to various embodiments, a method for controlling a radio communication device may be provided. The method may include: sending data to another radio communication device; and receiving from the other radio communication device an indication, wherein the indication may include or may be at least one of an indication indicating reception of data sent by the data sender and an indication indicating that the other radio communication device is ready for receiving data. The data sender may be configured to send data to the other radio communication device if the receiver does not receive the indication.

Brief Description of the Drawings

[0017] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings, in which:

FIG. 1 shows a communication system according to various embodiments;

FIG. 2 shows a radio communication device according to various embodiments;

FIG. 3 shows a flow diagram illustrating a method for controlling a radio communication device according to various embodiments;

FIG. 4 shows a radio communication device according to various embodiments;

FIG. 5 shows a flow diagram illustrating a method for controlling a radio communication device according to various embodiments;

FIG. 6 shows a radio communication device according to various embodiments;

FIG. 7 shows a flow diagram illustrating a method for controlling a radio communication device according to various embodiments;

FIG. 8 shows a radio communication device according to various embodiments;

FIG. 9 shows a flow diagram illustrating a method for controlling a radio communication device according to various embodiments;

FIG. 10 shows a communication system according to various embodiments; FIG. 1 1 shows a format of a packet according to various embodiments;

FIG. 12A and FIG. 12B show flow diagrams illustrating a downlink transmission following a four- way handshake according to various embodiments;

FIG. 13A and FIG. 13B show flow diagrams illustrating a downlink transmission following a two-way handshake according to various embodiments; and

FIG. 14A and FIG. 14B show flow diagrams illustrating a downlink transmission following a clear-to-send-to-self-handshake according to various embodiments.

Description

[0018] Embodiments described below in context of the devices are analogously valid for the respective methods, and vice versa.

[0019] In this context, the radio communication device as described in this description may include a memory which is for example used in the processing carried out in the radio communication device. A memory used in the embodiments may be a volatile memory, for example a DRAM (Dynamic Random Access Memory) or a nonvolatile memory, for example a PROM (Programmable Read Only Memory), an EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), or a flash memory, e.g., a floating gate memory, a charge trapping memory, an MRAM (Magnetoresistive Random Access Memory) or a PCRAM (Phase Change Random Access Memory).

[0020] In this context, a radio communication device may be a mobile radio communication device, like a mobile phone, a user equipment (UE), or a mobile station, or a client, or may be a base station, for example a wireless access point, for example a wireless local area network access point or a metropolitan area access point. An access point (AP) may be for example a WiFi AP, a WLAN AP, or a metropolitan area system AP.

[0021] In an embodiment, a "circuit" may be understood as any kind of a logic implementing entity, which may be special purpose circuitry or a processor executing software stored in a memory, firmware, or any combination thereof. Thus, in an embodiment, a "circuit" may be a hard-wired logic circuit or a programmable logic circuit such as a programmable processor, e.g. a microprocessor (e.g. a Complex Instruction Set Computer (CISC) processor or a Reduced Instruction Set Computer (RISC) processor). A "circuit" may also be a processor executing software, e.g. any kind of computer program, e.g. a computer program using a virtual machine code such as e.g. Java. Any other kind of implementation of the respective functions which will be described in more detail below may also be understood as a "circuit" in accordance with an alternative embodiment.

[0022] The Cellular Wide Area radio communication network in this description may include but is not limited to a communication network based on one of the following technologies, e.g. a Global System for Mobile Communications (GSM) radio communication technology, a General Packet Radio Service (GPRS) radio communication technology, an Enhanced Data Rates for GSM Evolution (EDGE) radio communication technology, a Third Generation Partnership Project (3GPP) radio communication technology (e.g. UMTS (Universal Mobile Telecommunications System) (e.g., W-CDMA (Wideband Code Division Multiple Access)), FOMA (Freedom of Multimedia Access), 3 GPP LTE (Long Term Evolution), 3 GPP LTE Advance (Long Term Evolution Advance)), and/or a Fourth Generation (4G) radio communication technology .

[0023] The Short Range radio communication network in this description may include but is not limited to one of the following communication networks, e.g. Wireless Local Area Network (LAN) radio communication (e.g. according to an IEEE 802.11 (e.g. IEEE 802.1 1η) radio communication standard, e.g. WiFi), Bluetooth radio communication. _l

[0024] The Metropolitan Area System radio communication network in this description may include but is not limited to one of the following communication network, e.g. wireless Metropolitan Area Network (MAN) radio communication, Worldwide Interoperability for Microwave Access (WiMax) (e.g. according to an IEEE 802.16 radio communication standard), Wireless Broadband (WiBro).

[0025] In an embodiment, the wireless access point is a long range WiFi access point providing a radio range of more than 100m. Examples of the radio ranges may include 100m, 200m, 500m, 800m, etc. In another embodiment, the wireless access point is a long range WiFi access point providing a radio range of more than 1km. Depending on the power limits, and if regulators allow more power, the wireless access point may provide an even longer radio range, e.g. beyond 1km, 2km, 5km, 10km, 50km, etc. in other embodiments.

[0026] According to various embodiments, methods and devices may be provided which may be used to solve the asymmetric WiFi link between AP and stations encountered in the 3 G- WiFi offloading networks. [0027] WIFI offloading may become a critical technology for the service provider to shift the mobile data service demand from the legacy cellular networks. However, the link asymmetric caused by transmission power difference at WIFI AP and mobile stations may limit the coverage of WIFI AP and may increase the overall network deployment cost. Various embodiments may be proposed to improve the coverage of WIFI AP in 3G WIFI offloading networks. These approaches may cover various possible solutions that may help in delivering the necessary information required for the WIFI uplink. Various technology such as TDMA scheduling, PLCP header with high gain signals, multi-radio multi-channel technology and CTS relaying may be used to extend the communication range. The various embodiments may solve the asymmetric link issue encountered in the cellular- WIFI data offloading.

[0028] FIG. 1 shows a communication system 100 according to various embodiments.

[0029] In this example, a communication system is described in the context of 3G- WiFi. However, it is to be noted that devices and methods of various embodiments may be applied for other types of Cellular Wide Area radio communication network and other types of Short Range radio communication networks or Metropolitan Area System radio communication networks.

[0030] A mobile client 102 (which may also be referred to as a radio communication device) may include two or more interfaces for network access. In an embodiment, the mobile client 102 includes a first interface, e.g. a 3G interface 106, enabling access to a Cellular Wide Area radio communication network, e.g. a 3G network. The mobile client 102 further includes a second interface providing access to a Short Range radio communication network or a Metropolitan Area System radio communication network, such as Wireless LAN or Wireless MAN. In this embodiment, the second interface is a WiFi (also referred to as 802.1 la/b/g/n) interface 104. Examples of the mobile client device 102 include but are not limited to handphones, smartphones, tablet computers, PDA and handheld game consoles.

[0031] The mobile client device 102 connects to the 3G network in a standard manner via the 3G RAN (Radio Access Network) 120. The mobile client device 102 connects to a desired WiFi AP 108 selected out of a plurality of WiFi APs 108 and 110 through its WiFi interface 104 using the standard point-to-multipoint protocol. In the example of FIG. 1 , the distance between the mobile device 102 and the WiFi AP 108 is depicted as 1 km, in which the WiFi AP 108 is a long range WiFi AP. However, any communication link distance shorter than 1 km is also possible in other embodiments. When the distance between the mobile client device 102 and the WiFi AP 108 is long, the mobile client 102 may receive downlink packets/frames from the WiFi AP 108, but the uplink transmission to the WiFi AP 108 may not be successful due to the RF power level of the mobile client 102 using the conventional offload method, as discussed above. In an embodiment, the WiFi AP 108 may be provided with extra features to handle the asymmetrical WiFi uplink and downlink communication, as will be described in detail below.

[0032] A SGSN (Serving GPRS Support Node) 118 may be provided between the 3G RAN 120 and a GGSN (Gateway GPRS Support Node) 1 16 for delivery of data packets from and to the mobile client device 102. The GGSN 116 may be connected to the WiFi AP 108 via the Internet. The GGSN 116 may also be connected directly to the Wireless APs 108, 110 through an optional link 122 as shown in FIG. 1.

[0033] A 3G-WiFi offload server 1 14 may be provided, which may be located on the Internet or located in the 3G network being connected with the GGSN 116 through an optional link 124. The 3G-WiFi offload server 114 may be configured to aid in the coordination of the uplink and downlink communication between the WiFi AP 108 and the mobile client 102. In an embodiment, the 3G-WiFi offload server 1 14 may be co- located with the distributed long range WiFi APs 108, 110. The 3G WiFi offload server 114 may be connected to the Internet 112. The WiFi AP 108, 1 10 may be connected to the Internet 1 12.

[0034] The mobile data offload method between a Cellular Wide Area radio communication network and another network including a Short Range radio communication network or a Metropolitan Area System radio communication network in accordance with various embodiments as described below is implemented in the architecture of FIG. 1.

[0035] FIG. 2 shows a radio communication device 200 according to various embodiments. The radio communication device 200 may include a receiver 202 configured to receive data from another radio communication device (not shown) using a first radio communication channel. The radio communication device 200 may further include an indication generation circuit 204 configured to generate an indication indicating a reception property of the data received from the other radio communication device. The radio communication device 200 may further include a sender 206 configured to send the indication to the other radio communication device using a second radio communication channel. At least one of the first radio communication channel and the second radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network and a metropolitan area system radio communication network. The receiver 202, the indication generation circuit 204 and the sender 206 may be coupled with each other, for example by a coupling 208, for example an electrical coupling or optical coupling, like an electrical line or an optical line, or any other device configured to transmit electrical signals or optical signals, for example a cable.

[0036] According to various embodiments, the radio communication channel according to at least one of a short range radio communication and a metropolitan area system radio communication may include or may be a radio communication channel according to an IEEE 802.11 radio communication.

[0037] According to various embodiments, the first radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network communication and a metropolitan area system radio communication network communication.

[0038] According to various embodiments, the second radio communication channel may include or may be a radio communication channel according to a cellular radio network.

[0039] According to various embodiments, the radio communication device 200 may include or may be a mobile radio communication device. [0040] According to various embodiments, the other radio communication device may include or may be a wireless access point, for example a WiFi AP, a WLAN AP, or a metropolitan area system AP.

[0041] According to various embodiments, the first radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network and a metropolitan area system radio communication network; the second radio communication channel may include or may be a radio communication channel according to a cellular radio network; the radio communication device may include or may be a mobile radio communication device; the other radio communication device may include or may be a wireless access point; and the sender may further be configured to send the indication to the wireless access point using the radio communication channel according to a cellular radio network and a communication from the network of a mobile operator of the cellular radio network to the wireless access point.

[0042] According to various embodiments, the indication may be indicating a reception of the data received from the other radio communication device

[0043] According to various embodiments, the indication may include or may be an ACK signal.

[0044] According to various embodiments, the indication may be indicating a status of a channel on which the data has been received from the other radio communication device. [0045] According to various embodiments, the first radio communication channel may include or may be a radio communication channel on a first frequency band according to an wireless local area network radio communication.

[0046] According to various embodiments, the second radio communication channel may include or may be a radio communication channel on a second frequency band according to an wireless local area network radio communication.

[0047] According to various embodiments, the first radio communication channel may include or may be a radio communication channel on a first frequency band according to an wireless local area network radio communication; the second radio communication channel may include or may be a radio communication channel on a second frequency band according to an wireless local area network radio communication; and the first frequency band may include or may be frequencies lower than frequencies of the second frequency band.

[0048] According to various embodiments, the first radio communication channel may include or may be a radio communication channel on a first frequency band according to an wireless local area network radio communication; the second radio communication channel may include or may be a radio communication channel on a second frequency band according to an wireless local area network radio communication; and the first frequency band may include or may be frequencies higher than frequencies of the second frequency band.

[0049] FIG. 3 shows a flow diagram 300 illustrating a method for controlling a radio communication device according to various embodiments. In 302, data may be received from another radio communication device using a first radio communication channel. In 304, an indication indicating a reception property of the data received from the other radio communication device may be generated. In 306, the indication may be sent to the other radio communication device using a second radio communication channel. At least one of the first radio communication channel and the second radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network communication and a metropolitan area system radio communication network communication.

[0050] According to various embodiments, the radio communication channel according to at least one of a short range radio communication and a metropolitan area system radio communication may include or may be a radio communication channel according to an IEEE 802.11 radio communication.

[0051] According to various embodiments, the first radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network communication and a metropolitan area system radio communication network communication.

[0052] According to various embodiments, the second radio communication channel may include or may be a radio communication channel according to a cellular radio network.

[0053] According to various embodiments, the radio communication device may include or may be a mobile radio communication device.

[0054] According to various embodiments, the other radio communication device may include or may be a wireless access point. [0055] According to various embodiments, the first radio communication channel may include or may be a radio communication channel according to at least one of a short range radio communication network communication and a metropolitan area system radio communication network communication; the second radio communication channel may include or may be a radio communication channel according to a cellular radio network; the radio communication device may include or may be a mobile radio communication device; the other radio communication device may include or may be a wireless access point; and the sender may further be configured to send the indication to the wireless access point using the radio communication channel according to a cellular radio network and a communication from the network of a mobile operator of the cellular radio network to the wireless access point.

[0056] According to various embodiments, the indication may be indicating a reception of the data received from the other radio communication device.

[0057] According to various embodiments, the indication may include or may be an ACK signal.

[0058] According to various embodiments, the indication may be indicating a status of a channel on which the data has been received from the other radio communication device.

[0059] According to various embodiments, the first radio communication channel may include or may be a radio communication channel on a first frequency band according to an wireless local area network radio communication. [0060] According to various embodiments, the second radio communication channel may include or may be a radio communication channel on a second frequency band according to an wireless local area network radio communication.

[0061] According to various embodiments, the first radio communication channel may include or may be a radio communication channel on a first frequency band according to an wireless local area network radio communication; the second radio communication channel may include or may be a radio communication channel on a second frequency band according to an wireless local area network radio communication; and the first frequency band may include or may be frequencies lower than frequencies of the second frequency band.

[0062] According to various embodiments, the first radio communication channel may include or may be a radio communication channel on a first frequency band according to an wireless local area network radio communication; the second radio communication channel may include or may be a radio communication channel on a second frequency band according to an wireless local area network radio communication; and the first frequency band may include or may be frequencies higher than frequencies of the second frequency band.

[0063] FIG. 4 shows a radio communication device 400 according to various embodiments. The radio communication device 400 may include a data sender 402 configured to send, using a first transmission mode, data to another radio communication device (not shown). The radio communication device 400 may further include an indication sender 404 configured to send, using a second transmission mode, to the other radio communication device an indication. The indication may include or may be at least one of an indication indicating reception of data sent from the other radio communication device and an indication indicating that the radio communication device is ready for receiving data. The second transmission mode may include a transmission mode of higher transmission robustness than the first transmission mode. The data sender 402 and the indication sender 404 may be coupled with each other, for example by a coupling 406, for example an electrical coupling or optical coupling, like an electrical line or an optical line, or any other device configured to transmit electrical signals or optical signals, for example a cable. It will be understood that data may include or may be any kind of data, such as use data, user data, or any other kind of data, for example data different from the indication.

[0064] According to various embodiments, the second transmission mode may include or may be a transmission mode using a modulation mode of higher transmission robustness than a modulation mode of the first transmission mode.

[0065] According to various embodiments, the second transmission mode may include or may be a transmission mode using a coding rate of higher transmission robustness than a coding rate of the first transmission mode.

[0066] According to various embodiments, the second transmission mode may include or may be a transmission mode using a higher processing gain than a processing gain of the first transmission mode.

[0067] According to various embodiments, the radio communication device 400 may include or may be a mobile radio communication device.

[0068] According to various embodiments, the other radio communication device may include or may be a wireless access point. [0069] According to various embodiments, the indication may include or may be at least one of an ACK signal and a CTS signal.

[0070] According to various embodiments, the data sender 402 and the indication sender 404 may be configured to send using a media access control frame.

[0071] According to various embodiments, the media access control frame may include a physical layer convergence protocol header field and a physical layer service data unit field. According to various embodiments, the radio communication device 400 may be configured to send the physical layer service data unit field with a robustness of at least essentially a robustness of the physical layer convergence protocol header field, if the physical layer service data unit field includes the indication.

[0072] According to various embodiments, the media access control frame may include a signal field. According to various embodiments, the indication sender 404 may be configured to send the indication directly before the signal field and/ or directly after the signal field.

[0073] According to various embodiments, the media access control frame may include a physical layer convergence protocol preamble field. According to various embodiments, the indication sender 404 may be configured to send the physical layer convergence protocol preamble field as the indication.

[0074] FIG. 5 shows a flow diagram 500 illustrating a method for controlling a radio communication device according to various embodiments. In 502, data may be sent using a first transmission mode to another radio communication device. In 504, an indication may be sent using a second transmission mode to the other radio communication device. The indication may include or may be at least one of an indication indicating reception of data sent from the other radio communication device and an indication indicating that the radio communication device is ready for receiving data. The second transmission mode may include or may be a transmission mode of higher transmission robustness than the first transmission mode. It will be understood that data may include or may be any kind of data, such as use data, user data, or any other kind of data, for example data different from the indication.

[0075] According to various embodiments, the second transmission mode may include or may be a transmission mode using a modulation mode of higher transmission robustness than a modulation mode of the first transmission mode.

[0076] According to various embodiments, the second transmission mode may include or may be a transmission mode using a coding rate of higher transmission robustness than a coding rate of the first transmission mode.

[0077] According to various embodiments, the second transmission mode may include or may be a transmission mode using a higher processing gain than a processing gain of the first transmission mode.

[0078] According to various embodiments, the radio communication device may include or may be a mobile radio communication device.

[0079] According to various embodiments, the other radio communication device may include or may be a wireless access point.

[0080J According to various embodiments, the indication may include or may be at least one of an ACK signal and a CTS signal.

[0081] According to various embodiments, the method may further include sending the data and the indication using a media access control frame. [0082] According to various embodiments, the media access control frame may include a physical layer convergence protocol header field and a physical layer service data unit field. According to various embodiments, the method further include sending the physical layer service data unit field with a robustness of at least essentially a robustness of the physical layer convergence protocol header field, if the physical layer service data unit field includes the indication.

[0083] According to various embodiments, the media access control frame may include a signal field. According to various embodiments, the method may further include sending the indication at least one of directly before the signal field and directly after the signal field.

[0084] According to various embodiments, the media access control frame may include a physical layer convergence protocol preamble field. According to various embodiments, the method may further include sending the physical layer convergence protocol preamble field as the indication.

[0085] FIG. 6 shows a radio communication device 600 according to various embodiments. The radio communication device 600 may include a receiver 602 configured to receive from a first other radio communication device an indication. The indication may include or may be at least one of an indication indicating reception of data sent from a second other radio communication device and an indication indicating that the first other radio communication device is ready for receiving data. The radio communication device 600 may further include a sender 604 configured to send the received indication to the second other radio communication device. The receiver 602 and the sender 604 may be coupled with each other, for example by a coupling 606, for example an electrical coupling or optical coupling, like an electrical line or an optical line, or any other device configured to transmit electrical signals or optical signals, for example a cable.

[0086] According to various embodiments, the indication may include or may be at least one of an ACK signal and a CTS signal.

[0087] According to various embodiments, the radio communication device 600 may include or may be a mobile radio communication device.

[0088] According to various embodiments, the first other radio communication device may include or may be a mobile radio communication device.

[0089] According to various embodiments, the second other radio communication device may include or may be a wireless access point.

[0090] FIG. 7 shows a flow diagram 700 illustrating a method for controlling a radio communication device according to various embodiments. In 702, an indication may be received from a first other radio communication device. The indication may include or may be at least one of an indication indicating reception of data sent from a second other radio communication device and an indication indicating that the first other radio communication device is ready for receiving data. In 704, the received indication may be sent to the second other radio communication device.

[0091] According to various embodiments, the indication may include or may be at least one of an ACK signal and a CTS signal.

[0092] According to various embodiments, the radio communication device may include or may be a mobile radio communication device. [0093] According to various embodiments, the first other radio communication device may include or may be a mobile radio communication device.

[0094] According to various embodiments, the second other radio communication device may include or may be a wireless access point.

[0095] FIG. 8 shows a radio communication device 800 according to various embodiments. The radio communication device 800 may include a data sender 802 configured to send data to another radio communication device (not shown). The radio communication device 800 may further include a receiver 804 configured to receive from the other radio communication device an indication. The indication may include or may be at least one of an indication indicating reception of data sent by the data sender and an indication indicating that the other radio communication device is ready for receiving data. The data sender 802 may be configured to send data to the other radio communication device if the receiver 804 does not receive the indication. The data sender 802 and the receiver 804 may be coupled with each other, for example by a coupling 806, for example an electrical coupling or optical coupling, like an electrical line or an optical line, or any other device configured to transmit electrical signals or optical signals, for example a cable.

[0096] According to various embodiments, the indication may include or may be at least one of an ACK signal and a CTS signal.

[0097] According to various embodiments, the radio communication device 800 may include or may be a wireless access point.

[0098] According to various embodiments, the other radio communication device may include or may be a mobile radio communication device. [0099] FIG. 9 shows a flow diagram 900 illustrating a method for controlling a radio communication device according to various embodiments. In 902, data may be sent to another radio communication device. In 904, an indication may be received from the other radio communication device. The indication may include or may be at least one of an indication indicating reception of data sent by the data sender and an indication indicating that the other radio communication device is ready for receiving data. The data sender may be configured to send data to the other radio communication device if the receiver does not receive the indication.

[00100] According to various embodiments, the indication may include or may be at least one of an ACK signal and a CTS signal.

[00101] According to various embodiments, the radio communication device may include or may be a wireless access point.

[00102] According to various embodiments, the other radio communication device may include or may be a mobile radio communication device.

[00103] According to various embodiments, devices and methods may be provided for asymmetrical Cellular- WiFi offload for long range WiFi networks.

[00104] As smart phones become more and more popular, mobile data traffic has been growing rapidly in recent years. According to some forecasts, mobile data traffic will grow much faster than fixed data traffic over next five years. On the other hand, the expansion of the network capacity will not likely be able to keep up with the growth pace of data traffic due to cost of network replacement and shortage of radio resources.

[00105] For almost all the service providers (SPs), it may be difficult to satisfy the demand on network capacity from mobile data traffic solely by upgrading existing equipment or building up more new cells due to the cost and shortage of radio resources. On the other hand, since almost every smart phone nowadays comes with a WIFI chipset, a promising solution may be for the service providers to build up WIFI networks and offload as much as possible cellular data traffic to WIFI. This may be because the cost on deploying WIFI hot spot is relatively lower and the corresponding radio frequency band may be free. Millions of APs are expected to be deployed by SPs in coming years.

[00106] The cost savings with WIFI offload may be significant. SPs deploying a multi-access (WIFI and 3G) offload strategy can expect savings in the range of 20 to 25 per cent per annum. In the US market, service providers might save between $30 and $40 billion per year by 2013.

[00107] It has already been proved that WIFI offload can help SPs provide better mobile data service with lower costs. However, a number of challenges such as IP address changing, asymmetric link etc. still prevent the WIFI offload technology from being fully exploited. A set of solutions is provided for the coverage problem caused by the WIFI asymmetric link phenomenon.

[00108] WIFI technology nowadays plays an important role in the data offloading for the cellular networks. The coverage of a WIFI AP may vary from a few hundred meters to 1 kilometer. The signal propagation may be determined by the radio transmission power and antenna gain. The overall emitted transmission power is under government regulations.

[00109] The transmit power limit for WIFI normally ranges from 1 to 4W EIRP (equivalent isotropically radiated power) for isotropic PMP mode depending on country. Such power limit may normally be sufficient for an AP to reach a coverage distance of around 1km, depending on the propagation characteristics. On the other hand, the power level in hand phone is normally lower (for example about 50 mW) and can only reach less than 50m in indoor environment. The difference in transmission range may cause an asymmetric connectivity between APs and hand phones and further may cause the coverage of APs to be shortened by a few folds. Due to such asymmetric connectivity, the effectiveness of WIFI offloading can be significantly affected. Thus, the coverage of an AP may not be fully utilized.

[00110] Asymmetric WIFI connectivity may significantly reduce the effectiveness of Cellular- WIFI offloading. A mobile station may receive data from an access point (AP) but it may not send back messages to the AP via the WIFI link. Without feedback from the mobile station, the communication between the AP and mobile station may not function properly, for example, when AP sends out RTS (ready to send) but does not receive uplink CTS (clear to send), it may not be allowed to transmit data since this is considered as collision or channel being occupied by other devices. The asymmetric link also may cause timeout for the association between mobile station and AP. Therefore, communication approaches may be desired to be adopted so that the AP can still be aware the status of mobile station when the link between AP and mobile station becomes asymmetric. Furthermore, the scheduling mechanism defined in the current standard may need to be updated to take the asymmetric link into account.

[00111] According to various embodiments, various devices and methods may be provided which enable APs and mobile stations to continue the data communication even if the downlink and uplink between them are asymmetric. The devices and methods may include one or more of the following: TDMA-like transmissions by AP; changing the PLCP header format or introducing high gain signals; using multi-channel multi-radio technology; and CTS/ACK relaying.

[00112] FIG. 10 shows a communication system according to various embodiments. The reference network architecture for various devices and methods according to various embodiments shown in FIG. 10 is similar to the communication system according to various embodiments shown in FIG. 1, and similar elements may be denoted with the same reference signs and duplicate description may be omitted. FIG. 10 shows an overall network architecture for the cellular WIFI offloading. While in FIG. 10, the 3G (third generation) network is used as a representation of a cellular network, in general, any other cellular networks may be able to replace the 3G networks above. The term WIFI herein may be understood for example as IEEE 802.1 1.

[00113] A mobile client 1002 may have a plurality of WiFi transceivers 1004, 1006. A plurality of WiFi AP 1008, 1010 may be provided, each having a plurality of WiFi transceivers. A WiFi link 1012 may be provided to operate on a lower radio band, and a

WiFi link 1014 may be provided to operate on a higher radio band.

[00114] In the following, devices and methods according to various embodiments will be described which work in a TDMA (time division multiple access) manner.

[00115] Data packets from the network or an access point (AP) may be sent to mobile station via IEEE 802.11 link such as 802.11a b/g/n/ah and packets from mobile station, including control messages from mobile station to network may be sent via the 3G link.

This may be different from current communication arrangement where only one link, either 3G or IEEE 802.11, is used for both uplink and downlink. [00116] To avoid collisions and support the communication described above, the following modifications may be provided to the existing protocols.

[00117] 1) The AP may be desired to disregard (or disable) the acknowledgement from rnobile station on the link since the mobile station cannot reach the AP via the WIFI uplink. The transmission reliability may be ensured by upper layer protocols such as

TCP, which provides retransmission capability at the transport layer.

[00118] 2) The AP may divide the channel time between two beacons into virtual slots.

[00119] 3) The AP may reserve some slots persistently over a few frames and may declare the scheduling to the neighbour APs and stations within its coverage so that they are not going to use these slots for transmission. The scheduling information can be transmitted in the beacon frames.

[00120] 4) Mobile station may report the status of the channel from AP to mobile station via the cellular link so that AP may make necessary adjustments of the channel configuration such as modulation and coding, for example.

[00121] In the following, a CSMA (Carrier Sense Multiple Access)/CA (collision avoidance) approach using modified uplink CTS / ACK will be described.

[00122] When using WIFI as downlink and mobile station cannot reach the AP via the uplink, the communication may not be performed properly since sometimes without CTS from uplink, the AP is not allowed to transmit data on the downlink. And also, without

ACK (acknowledgement), the AP cannot react to the packet losses promptly.

[00123] To solve the issue, the transmission power at the mobile station side may be increased when it transmits CTS/ACK so that they can reach AP, However, how far the CTS/ACK can reach is subject to hardware capability and the power regulations. Using high power usually may add additional cost on hardware.

[00124] The AP may be able to decode the PLCP header but may encounter errors in decoding CTS/ACK packets. According to various embodiments, the PLCP (Physical Layer Convergence Protocol) may be redesigned.

[00125] FIG. 1 1 shows a format 1 100 of a packet (for example the PLCP packet) according to various embodiments.

[00126] FIG. 1 1 shows the frame format 1 100 for an 802.1 1 MAC (Media Access Control) frame. According to various embodiments, the PLCP may be redesigned and some additional bits may be added in as indication for CTS/ACK. A PLCP header may be transmitted with BPSK (Binary phase-shift keying) modulation and Vi coding rate. The RATE field in the frame may specify the modulation and coding scheme used for PSDU (Physical layer Service Data Unit), which may carry the CTS or ACK. Since the PSDU may be transmitted with higher modulation than the PLCP header, the AP may be able to decode the PLCP header but encounter errors in decoding CTS/ACK packets. According to various embodiments, the modulation and coding rates of PSDU part may be lowered to the same level as PLCP header when asymmetric scheme is used and CTS/ACK is sent on the uplink. According to various embodiments, 2 or more OFDM symbols may be added right after SIGNAL or before SIGNAL field and encode MAC address and other possible control signal , on these OFDM symbols. The MC used on these two (or more) symbols may be the most robust ones. These two or more OFDM symbols shall be kept to lowest possible coding and modulation format. Mobile station can use these two symbols to carry the CTS and ACK information. Since the modulation and coding rate is low, CTS/ACK may reach further comparing to the case when they are transmitted according to the existing 802.1 1 specifications.

[00127] According to various embodiments, besides changing the format of PLCP header, there may be other alternatives that may help the AP to detect whether the channel is "clear to send" at the mobile station side.:

[00128] 1) The AP may send RTS and mobile client replies with CTS. The AP may be able to decode the PLCP preambles and/or PLCP header but may not decode the PSDU in the packet. The AP may use the PLCP preambles and/or PLCP header as an indication for CTS/ACK based on the timing relative to the RTS and data transmitted previously, for example by measuring the estimated receiving time of the signal indicating CTS/ACK. The signal indicating CTS/ACK may not be decoded properly at the baseband level.

[00129] 2) The mobile station may transmit a special signal with higher processing gain before or after CTS or between the preamble and SIGNAL, or after SIGNAL and before data as an indication for CTS and ACK. The AP may decode the high gain signal and infer whether CTS or ACK has been sent out by the mobile client or not.

[00130] In the following, a CSMA/CA approach with ignoring unheard CTS/ACK according to various embodiments will be described.

[00131] This approach may include of the following:

[00132] 1) In the downlink (DL), control/data messages may be transmitted using WiFi links.

[00133] 2) The AP may transmit data toward its associated stations using 4-way (RTS, CTS, Data, ACK), or 2-way (Data, ACK), or CTS-to-self handshaking mechanisms. To cater for the situations that the uplink CTS, ACK messages transmitted by an associated station cannot reach the AP, the AP may be configured to bypass the reception of these signals.

[00134] According to various embodiments, when DL data transmission over the WiFi link is based on the 4-way handshake, the AP may force a data transmission after it has transmitted TS message. This may happen even if the AP does not receive a CTS message from the targeted station. This is illustrated in FIG. 12A and FIG. 12B.

[00135] FIG. 12A and FIG. 12B show flow diagrams illustrating a downlink transmission following a four-way handshake according to various embodiments, for example DL transmission over WiFi channel following the 4-way handshake. In FIG. 12A, a flow diagram 1200 is shown, wherein a client 1204 (for example a radio communication device) is not busy (in other words: not receiving data from a hidden node 1202), and may respond to an RTS signal 1208 from an AP 1206 with an CTS signal 1210. However, the CTS signal 1210 may not reach the AP 1206. According to various embodiments, the AP 1206 may force a data transmission^ 12 to the client 1204. The client 1204 may respond with an ACK signal 1214, which also may not reach the AP 1206. In FIG. 12B, a flow diagram 1200 is shown, in which the client 1204 is busy; for example there is some ongoing transmission 1220 from the hidden node 1202. The AP 1206 may send an RTS signal 1218 to the client 1204, and after not receiving a CTS signal, the AP 1206 may force a data transmission 1222.

[00136] According to various embodiments, when DL data transmission over the WiFi link is based on the 2-way handshake, the AP may force a data transmission toward an associated station and may not react to a missing ACK from the receiving station. This is illustrated in FIG. 13 A and FIG. 13B.

[00137] FIG. 13A and FIG. 13B show flow diagrams illustrating a downlink transmission following a two-way handshake according to various embodiments, for example DL transmission over WiFi channel following the 2-way handshake. In FIG. 13A, a flow diagram 1300 is shown, wherein a client 1304 (for example a radio communication device) is not busy (in other words: not receiving data from a hidden node 1302). An AP 1306 may for a data transmission 1308. The client 1304 may send an ACK 1310, but the ACK may not be received by the AP 1306. FIG. 13B shows a flow diagram 1312, wherein the client 1304 is busy; for example there is some ongoing transmission 1314 from the hidden node 1302. The AP 1306 may for a data transmission 1316. The AP 1306 may be unsure if the data is received by the client 1304.

[00138] According to various embodiments, when DL data transmission over the WiFi link is based on the CTS-to-self handshake, the AP may force a data transmission toward an associated station after transmitting CTS message to itself, and may not react to a missing ACK from the receiving station. This is illustrated in FIG. 14A and FIG. 14B.

[00139] FIG. 14A and FIG. 14B show flow diagrams illustrating a downlink transmission following a clear-to-send-to-self-handshake according to various embodiments, for example DL transmission over WiFi channel following the CTS-to-self handshake. In FIG. 14A, a flow diagram 1400 is shown, wherein a client 1404 (for example a radio communication device) is not busy (in other words: not receiving data from a hidden node 1402). An AP 1406 may force a data transmission 1410 after sending CTS-to-self signal 1408. The client 1404 may respond with an ACK signal 1412, but the ACK signal may not reach the AP 1406. FIG. 14B shows a flow diagram 1414, in which the client 1404 is busy; for example there is some ongoing transmission 1418 from the hidden node 1402. Still, the AP 1406 may force data transmission 1420 after having sent a CTS-to-self signal 1416.

[00140] In the following, device and methods using multiple radio multiple channel (MRMC) will be described.

[00141] According to various embodiments, devices and methods for solving the asymmetric link issue encountered in the offloading with WIFI may be using multi-radio technology. The downlink (from AP to mobile station) and uplink (from mobile station to AP) may work on different pairs of WIFI radios, for example like described above with reference to FIG. 10. Each pair of radios may work on a different radio frequency. Both data and control signals may be transmitted on the two pairs of radios.

[00142] According to various embodiments, one or more of the following configurations may be provided:

[00143] Option I: Cellular network on the mobile station may be used as uplink data communication while either one or two WIFI radios (High and Low frequency) are used for downlink data communication.

[00144] Option II: The WIFI radio operating at lower frequency may be used for uplink data communication while the WIFI radio operating in higher frequency may be used for downlink data communication. Data communication on any WIFI radio may include the MAC layer data and signaling (E.g. RTS/CT S/D AT A/ AC K) .

[00145] Option III: The WIFI radio operating at lower frequency may be used for uplink (mobile to AP) data communication and the MAC layer signaling (e.g. CTS/ACK) for the WIFI radio operating in higher frequency (which may be used for downlink data transmission). The WIFI radio operating in higher frequency may be used only for downlink data communication, from AP to mobile ^"station. The CTS/ACK transmitted by the mobile station with the higher frequency radio may not reach the AP.

[00146] Option IV: The WIFI radio operating at lower frequency may be used for uplink (mobile to AP) MAC layer signaling (for example CTS/ACK) for the WIFI radio operating in higher frequency (which may be used for downlink data transmission). The WIFI radio operating in higher frequency may be used only for downlink data communication from AP to mobile station. In such a scenario, the CTS/ACK transmitted by the mobile station with the higher frequency radio may not reach the AP. In this option, the cellular network may be used for uplink data communication.

[00147] In the options (I-IV) described above, data communication may be referred as OSI (Open Systems Interconnection) layer 3 communications and may not to be confused by the MAC layer DATA frame.

[00148] In the embodiments described above, radios operating on the higher bandwidth/frequency, may be IEEE 802.11 a/b/g/nradios, and the radios working on a lower bandwidth/frequency may be sub-1 GHz radios such as 802.11 ah.

[00149] To illustrate option IV, while using a 2-way handshake, the AP may use the radio on the higher bandwidth/frequency to transmit a DATA frame to the mobile station. The mobile station may send back an ACK frame on either the lower frequency radio only or both the lower and higher frequency radios. It is to be noted that the signals transmitted with lower radio frequency may reach further comparing to the distance when it is transmitted with higher radio frequency. Therefore, multi-radio and multi-channel technology may provide a viable solution for the asymmetric link issue encountered in the data offloading for 3G networks.

[00150] According to various embodiments, an implementation of the above described embodiments may include a collaboration and communication at MAC layer between two 802.1 1 MAC entities within the same AP and mobile station. This communication need not be achieved through a wireless channel. The communication may be implemented with function calls inside the same computer operating system controlling the two radios.

[00151] According to various embodiments, to realize the design to satisfy the options III and IV, while using the 2-way handshake, the following approach may be used (which may be referred to as a Data-ACK mode):

[00152] 1) The AP and mobile station may configure the system so that radios at each side are aware of the existence of another radio. The radios within the same node may exchange MAC addresses and operating frequency with each other.

[00153] 2) When AP or mobile station detect that asymmetric channel exists in the communication between the AP and mobile station, the two nodes, AP and mobile station, may negotiate to use different frequencies for communication in different directions of the asymmetric link between AP and mobile stations.

[00154] 3) Once the negotiation is completed, the AP may send data packets to mobile station using the higher frequency radio, and the mobile station may send acknowledgement via another radio over lower frequency, for example the lower frequency radio. If the lower frequency radio on the mobile station sensed a busy channel and cannot send the ACK frame during the 2-way handshake cycle, it may defer to send this ACK frame at a later period. On the AP, the radio operating on lower frequency shall pass the received ACK frame to the radio operating on higher frequency via internal communication channel. The AP may retransmit some of the packets on the radio on the higher frequency if the acknowledgements are not received. The mobile station may either send both data and ACK via the radio working on lower frequency or transmit data packets over radio with lower frequency to the AP, and the AP may send back ACK via the radio on the higher frequency.

[00155] 4) The mobile station may report link quality of the channel for the higher frequency radio via the radio operating on lower frequency.

[00156] According to various embodiments, to protect data transmission, the AP may transmit an RTS on the radio operating on the higher radio frequency or on both radios.

[00157] According to various embodiments, to realize the design to satisfy the options III & IV, while using the 4-way handshake, the following approach may be used:

[00158] 1) The AP and mobile station may configure the system so that radios at each side are aware of the existence of another radio. The radios within the same node may exchange MAC addresses and operating frequency with each other.

[00159] 2) When the AP or mobile station detect that asymmetric channel exists in the communication between the AP and mobile station, the two nodes, AP and mobile station, may negotiate to use different frequencies for communication in different directions.

[00160] 3) When the AP intend to transmit a packet on the down link, which is operating on the higher radio frequency, it may transmit an RTS on the radio operating on the higher radio frequency. . [00161] 4) When the mobile station receives RTS from the radio operating on the higher frequency, and the radio channels on both higher frequency and lower frequency are clear, it may transmit a CTS back on both radios to indicate the channel on the higher frequency is clear to send. When either one of the radios do not sense a clear channel, both radios will not send the CTS frame.

[00162] 5) When the AP receives one or more CTS from mobile station (which will likely be from the radio operating on the lower frequency), the AP may send the MAC data frame as planned in the higher frequency radio. In case no CTS is received, the AP may not transmit and may start to back-off if necessary.

[00163] 6) When the mobile station receives the data frame (for example data packets) from the higher frequency radio correctly, it may transmit an ACK back to the AP via the radio operating on the lower frequency (for example only on via the radio operating on the lower frequency). The higher frequency radio may also transmit an ACK frame. If the lower frequency radio on the mobile station sensed a busy channel and cannot send the ACK frame during the 4-way handshake cycle, it may defer to send this ACK frame at a later period. On the AP, the radio operating on lower frequency may pass the received ACK frame to the radio operating on higher frequency via internal communication channel. The AP may retransmit some of the packets on the radio on the higher frequency if the acknowledgement was not received.

[00164] For options III & IV, while using the 4 way handshake, the AP and mobile station may also take the following actions (which may also be referred to as RTS-CTS- Data-ACK mode): [00165] 1) When the AP intends to transmit large packet on the down link, which is operating on the higher radio frequency, it may transmit RTSs on both radios.

[00166] 2) When the mobile station receives RTS from radio operating on the higher frequency, and the radio channels on both higher frequency and lower frequency are clear, it may transmit CTS back on both radios to indicate the channel on higher frequency is clear to send.

[00167] 3) When the AP receives one or more CTS from mobile station, likely from the radio operating on the lower frequency, the AP shall send the data frame as planned. In case no CTS is received, the AP may not transmit and may start to back-off if necessary.

[00168] 4) When the mobile station receives the data frame from the higher frequency radio correctly, it may transmit an ACK back to the AP via the radio operating on the lower frequency. The higher frequency radio may transmit an ACK frame. If the lower frequency radio on the mobile station sensed a busy channel and cannot send the ACK frame during the 4-way handshake cycle, it may defer to send this ACK frame at a later period. On the AP, the radio operating on lower frequency may pass the received ACK frame to the radio operating on higher frequency via internal communication channel. The AP may retransmit some of the packets on the radio on the higher frequency if the acknowledgement was not received.

[00169] In case AP has two radios but mobile station has only a single radio, to solve the asymmetric link issue, according to various embodiments, the radio on the mobile station may switch between different channels for receiving (on higher frequency) and transmitting (on lower frequency). [00170] According to various embodiments, a procedure to realize the above design may be provided as follows:

[00171] 1) The AP may configure the system so that radios at each side are aware the existence of another radio. The radios of the AP may exchange MAC address and operating frequency with each other.

[00172] 2) When the AP or mobile station detect that asymmetric link exists in the communication between the AP and mobile station, the two nodes, AP and mobile station, may negotiate to use different frequency for communication on different directions.

[00173] 3) Once both sides agree on using different frequency for transmitting on different directions, the AP may start to transmit data packet with radio on higher frequency and receive feedback packet from mobile station from the radio working on lower frequency.

[00174] 4) The mobile station may receive data from the channel on higher frequency for certain period. It may switch to the channel on lower frequency and send

acknowledgement to the AP. The AP may retransmit some of the packets on the radio on higher frequency based on the acknowledgement received from radio working on lower frequency.

[00175] 5) The mobile station may monitor on the beacons from AP on both frequency channel and may report the link quality on both channels back to the AP by transmitting on the lower frequency.

[00176] In the following, UL Relay of CTS and ACK according to various embodiments will be described. [00177] According to various embodiments, to overcome the problem of limited range of the uplink WiFi transmission, one or multiple stations may be provided to help forward CTS/ACK messages from a far-away station toward the AP. This procedure may include of the following:

[00178] 1) The AP may collect statistics regarding the range/distance between itself and associated stations.

[00179] a) In one embodiment, the collected statistics may be in terms of the received signal strength of control and/or data messages transmitted by the AP and received by an associated station. The associated station may measure the signal strength and may report to the AP through a direct uplink WiFi connection or through an uplink cellular connection.

[00180] b) In an embodiment, the collected statistics may be based on how control and/or data messages transmitted by an associated station are received at the AP. The AP may determine whether it can receive messages transmitted by the associated station, and if yes, at what signal strength.

[00181] 2) The AP may also collect statistics regarding the range/distance between a pair of its associated stations. The collected statistics may be in terms of received signal strength, or simply a binary parameter of whether the two stations can hear the control signals transmitted by each other.

[00182] 3) Based on the collected range and/ or distance statistics, for each station whose CTS/ACK messages cannot reach the AP directly, the AP may determine a set of in-between stations that may help forwarding the control messages. These in-between stations may be those that may reach the AP through direct uplink WiFi transmissions (or via another helping mobile station) while being able to receive a CTS/ACK signal from the far-away station. Based on this, the AP may let each of the associated stations know the list of faraway stations that "need help" in forwarding CTS/ACK messages. The AP may unicast and/or multicast/broadcast this list of need-help stations to the corresponding forwarding stations.

[00183] 4) Upon receiving a CTS/ACK message from one of the need-help stations, for example those within a list transmitted by the AP, a station shall attempt to forward this CTS/ACK message toward the AP. The forwarding station may access the channel using the CSMA/CA protocol. If during the channel-contention process, the forwarding station detects that the same CTS/ACK message has been forwarded by another station, the station may abandon the forwarding attempt.

[00184] 5) For what has been described under item 4 described above, a forwarding station may detect and receive a CTS/ACK message from a need-help station in the following ways:

[00185] a) The receiving of CTS/ACK message by the forwarding station may be reactive, for example the forwarding station may monitor the channel to detect if any relevant CTS/ACK message is transmitted by need-help stations.

[00186] b) The receiving of CTS/ACK message by the forwarding station may be proactive, for example based on pre-transmitted messages from the AP, the forwarding station may know in advance when a possible CTS/ACK message from a need-help station shall be transmitted. As an example, by listen to an RTS message transmitted by the AP, the forwarding station may know that this RTS is for a need-help station, and this need-help station may transmit a CTS message within a predefined time interval. [00187] 6) For what has been described under item 4) above, the AP may instruct different forwarding stations to contend for the channel (for example to forward the CTS/ACK message) with different priorities. This, for example, may be achieved through the use of different inter- frame spacing or back-off widow sizes as specified in 802.1 le.

[00188] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

Claims What is claimed is:

1. A radio communication device, comprising:

a data sender configured to send, using a first transmission mode, data to another radio communication device; and

an indication sender configured to send, using a second transmission mode, to the other radio communication device an indication, wherein the indication comprises at least one of an indication indicating reception of data sent from the other radio communication device and an indication indicating that the radio communication device is ready for receiving data;

wherein the second transmission mode comprises a transmission mode of higher transmission robustness than the first transmission mode.

2. The radio communication device of claim 1,

wherein the second transmission mode comprises a transmission mode using a modulation mode of higher transmission robustness than a modulation mode of the first transmission mode.

3. The radio communication device of claim 1 or 2, wherein the second transmission mode comprises a transmission mode using a coding rate of higher transmission robustness than a coding rate of the first transmission mode.

4. The radio communication device of any one of claims 1 to 3,

wherein the second transmission mode comprises a transmission mode using a higher processing gain than a processing gain of the first transmission mode.

5. The radio communication device of any one of claims 1 to 4,

wherein the radio communication device comprises a mobile radio communication device.

6. The radio communication device of any one of claims 1 to 5,

wherein the other radio communication device comprises a wireless access point.

7. The radio communication device of any one of claims 1 to 6,

wherein the indication comprises at least one of an ACK signal and a CTS signal.

8. The radio communication device of any one of claims 1 to 7,

wherein the data sender and the indication sender are configured to send using a media access control frame.

9. The radio communication device of claim 8, wherein the media access control frame comprises a physical layer convergence protocol header field and a physical layer service data unit field; and

wherein the radio communication device is configured to send the physical layer service data unit field with a robustness of at least essentially a robustness of the physical layer convergence protocol header field, if the physical layer service data unit field comprises the indication.

10. The radio communication device of claim 8 or 9,

wherein the media access control frame comprises a signal field; and

wherein the indication sender is configured to send the indication at least one of directly before the signal field and directly after the signal field.

11. The radio communication device of any one of claims 8 to 10,

wherein the media access control frame comprises a physical layer convergence protocol preamble field; and

wherein the indication sender is configured to send the physical layer convergence protocol preamble field as the indication.

12. A method for controlling a radio communication device, the method comprising: sending, using a first transmission mode, data to another radio communication device; and

sending, using a second transmission mode, to the other radio communication device an indication, wherein the indication comprises at least one of an indication indicating reception of data sent from the other radio communication device and an indication indicating that the radio communication device is ready for receiving data;

13. The method of claim 12,

14. The method of claim 12 or 13,

wherein the second transmission mode comprises a transmission mode using a coding rate of higher transmission robustness than a coding rate of the first transmission mode.

15. The method of any one of claims 12 to 14,

16. The method of any one of claims 12 to 15,

17. The method of any one of claims 12 to 16,

wherein the other radio communication device comprises a wireless access point.

18. The method of any one of claims 12 to 17,

19. The method of any one of claims 12 to 18, further comprising:

sending the data and the indication using a media access control frame.

20. The method of claim 19,

wherein the media access control frame comprises a physical layer convergence protocol header field and a physical layer service data unit field; and

wherein the method further comprises sending the physical layer service data unit field with a robustness of at least essentially a robustness of the physical layer convergence protocol header field, if the physical layer service data unit field comprises the indication.

21. The method of claim 19 or 20,

wherein the media access control frame comprises a signal field; and

wherein the method further comprises sending the indication at least one of directly before the signal field and directly after the signal field. The method of any one of claims 19 to 21,

wherein the method further comprises sending the physical layer convergence protocol preamble field as the indication.