JP2013516818A - Pico / Femtocell two-stage uplink synchronization - Google Patents

Abstract

A pico / femtocell two-phase uplink synchronization is provided.
The present invention provides a two-step uplink synchronization method used for uplink synchronization between a mobile station and a pico / femto base station, wherein the pico / femto base station is an overlay macro / micro base station. Are arranged together. During the first step, the pico / femto BS encodes the UL transmission timing advance offset information and broadcasts it on the broadcast channel. The MS decodes the received UL transmission timing advance offset information, and advances the uplink timing used for uplink ranging or reference code transmission based on the decoded offset value. During the second step, the MS and the pico / femto BS perform normal uplink synchronization and uplink access. In one example, UL transmission timing advance offset information indicates a round-trip propagation time of a radio signal between a pico / femto base station and an overlay macro / micro base station. By using a two-step uplink synchronization method, a unified synchronous ranging channel can be used for pico / femtocell ranging and UL access, reducing interference.
[Selection] Figure 8

Description

  This application is based on US Provisional Application No. 61/293424 entitled “A Two-Step Scheme for Uplink Synchronization in Femtocell,” filed on Jan. 8, 2010, US Code No. 35/119. We claim priority under the article, the contents of which are incorporated herein by reference.

  The present invention relates to wireless network communication, and in particular to pico / femtocell uplink synchronization in a wireless mobile communication system.

  Picocell and femtocell deployments are important in next generation (4G) wireless mobile communication systems, for example WiMAX 2.0 systems defined by IEEE 802.16m and LTE-advanced systems defined by 3GPP Release 10 It is a feature. The pico / femtocell arrangement enhances wireless mobile indoor service, macro and / or micro base station offload traffic, and compensation and reduces outdoor service coverage holes. When a pico / femto cell is deployed as an overlay macro / micro cell, network timing synchronization becomes an important issue, especially in the context of co-channel deployment. Network timing synchronization should be maintained and radio signals from pico / femto base stations and overlay macro / micro base stations should not interfere with each other when transmitted in the air.

  FIG. 1 (Prior Art) is a diagram showing a hierarchical cell structure of macro / micro cells and pico / femto cells in a cellular OFDM communication system 10. The cellular OFDM communication system 10 includes a macro / micro base station BS11, pico / femto base stations BS12 and BS13, and mobile stations MS14 and MS15. The two pico / femto base stations BS12 and BS13 have a small cell coverage, and the overlay macro / micro base station BS11 has a large cell coverage. In the example of FIG. 1, BS12 is located near BS11, and BS13 is separated from BS11. Mobile station MS14 is served by pico / femto BS13 and mobile station MS15 is served by macro / micro BS11. MS15 is far from its serving BS11, but close to the pico / femto BS13.

  FIG. 2 (Prior Art) is a diagram showing downlink, uplink subframe, and transmission timing in the cellular OFDM communication system 10. As shown in FIG. 2, in a time division duplex (TDD) system, the macro base station BS11 transmits data in the downlink (DL) subframe period and receives data in the uplink (UL) subframe period. To do. Each DL subframe is followed by a UL subframe, with a predetermined transmission switching gap (TTG) time between them, and each UL subframe is followed by a DL subframe, with a predetermined reception switching between the two. Gap (RTG) times are separated. The pico / femto base station BS12 is synchronized with the overlay BS11, but has substantially the same DL and UL transmission timing due to physical proximity to the BS11. The pico / femto base station BS13 is also synchronized with the overlay BS11 but has a delayed DL and UL transmission timing due to DL propagation delay. The mobile station MS15 served by the BS11 receives data in the DL subframe period and transmits data in the UL subframe period. At the serving BS11, after DL and UL synchronization, each DL subframe of MS15 is synchronized with each DL subframe of BS11 with DL propagation delay, and each UL subframe of MS15 is UL timing advance (timing advance) Synchronize with each UL subframe of BS11. As shown in FIG. 2, it can be seen that there is a timing difference between the UL subframes of pico / femto BS13 and MS15 due to DL propagation delay and UL timing advance.

  This requires the pico / femto BS13 to adjust its TTG to avoid possible uplink interference between the pico / femto mobile station (e.g., MS14) and the adjacent macro / micro mobile station (e.g., MS15). There is. If the timing difference is not an integer of the OFDM code, the uplink subframe is non-aiming, so in the absence of TTG adjustment in the pico / femtocell, the uplink reception of the pico / femto base station is the overlay macro / micro Interfered by uplink transmissions of neighboring mobile stations served by the base station. However, for pico / femtocell mobile stations that are handed over or camped, they do not know any TTG coordination. The TTG adjustment value cannot be known, and the understanding of the UL transmission timing between the mobile station and the pico / femto BS is different, leading to incomplete reception of uplink signals, for example, ranging signals of the pico / femto BS.

  In current IEEE 802.16m and 3GPP systems, a desynchronized ranging channel (RCH) or random access channel (RACH) is used for initial and handover ranging in pico / femtocells. FIG. 3 (Prior Art) is a diagram showing the desynchronized ranging channel 31 and the data channel 32 in the IEEE 802.16m OFDM system. As shown in FIG. 3, the pico / femto MS performs a ranging preamble transmission using a desynchronized ranging channel 31. The macro / micro MS performs data transmission using the data channel 32. The desynchronized ranging channel 31 has a long ranging cyclic prefix (RCP) length and guard time, and is used for timing differences in non-aiming uplink subframes between pico / femto MS and macro / micro MS. To adapt. However, this method has several drawbacks. First, it requires an asynchronous ranging channel and has a different CP length from the data channel in the same communication system. Second, the different CP lengths between the asynchronous ranging channel and the data channel cause interference with each other. As shown in FIG. 3, since the time domain structure of the asynchronous ranging channel 31 is different from that of the data channel 32, the orthogonality of the frequency domain between the two channels is destroyed. When the macro / micro MS transmits the data channel and the pico / femto MS transmits the ranging channel, the ranging performance in the pico / femto cell is greatly degraded. Third, the asynchronous ranging channel has a different physical structure and code sequence than the synchronous ranging channel. Thus, hardware complexity and pico / femto BS costs are not reduced unless a unified synchronous ranging channel is used.

  The present invention provides a two-stage uplink synchronization method used for uplink synchronization between a mobile station and a pico / femto base station, where the pico / femto base station is located together with an overlay macro / micro base station. Has been. During the first step, the pico / femto BS encodes the UL transmission timing advance offset information and broadcasts it on the broadcast channel. The MS decodes the received UL transmission timing advance offset information, and advances the uplink timing used for uplink ranging or reference code transmission based on the decoded offset value. During the second step, the MS and the pico / femto BS perform normal uplink synchronization and uplink access. By using a two-step uplink synchronization method, a unified synchronous ranging channel can be used for pico / femtocell ranging and UL access, reducing interference.

  In one example, UL transmission timing advance offset information indicates a round-trip propagation time of a radio signal between a pico / femto base station and an overlay macro / micro base station. In one example, the pico / femto BS encodes the UL transmission timing advance offset information into a single number indicating the UL transmission timing advance offset value. The MS receives the UL transmission timing advance offset information and decodes the UL transmission timing advance offset value. In the IEEE 802.16m WiMAX system, before introducing the normal UL synchronization process, it is proposed that the MS advances the ranging signal transmission timing based on the decoded offset value. In the 3GPP LTE / LTE-A system, it is proposed that the MS advances the reference signal transmission timing based on the decoded offset value before introducing the normal UL access process.

  Other embodiments and advantages are described in the detailed description below. This summary is not intended to define the invention. The invention is defined by the claims.

The accompanying drawings illustrate embodiments of the invention, in which like numerals refer to like elements.
FIG. 1 (Prior Art) shows a hierarchical cell structure of macro / micro cells and pico / femto cells in a cellular OFDM communication system. (Prior Art) It is a diagram showing downlink, uplink subframe and transmission timing in a cellular OFDM communication system. (Prior Art) It is a diagram showing an asynchronous ranging channel and a data channel in an IEEE 802.16m OFDM system. FIG. 2 shows a macro / micro cell and pico / femto cell hierarchical cell structure in a cellular OFDM / OFDMA communication system 40 according to one novel aspect. It is a figure which shows the downlink of the base station and mobile station in a hierarchical cell structure, an uplink sub-frame, and transmission timing. It is a figure which shows the downlink in the initial ranging process period of a pico / femto cell, an uplink sub-frame, and transmission timing. It is a figure which shows the downlink, uplink sub-frame, and transmission timing during the handover ranging process in a pico / femtocell. 2 is a flowchart of a method of two-stage uplink synchronization according to one novel aspect.

  Reference may describe in detail some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

  FIG. 4 is a diagram illustrating a hierarchical cell structure of macro / micro cells and pico / femto cells in a cellular OFDM / OFDMA communication system 40 according to one novel aspect. The cellular OFDM / OFDMA communication system 40 includes a macro / micro base station BS41, pico / femto base stations BS42 and BS43, and mobile stations MS44 and MS45. In general, pico / femto base stations have a small cell coverage and macro / micro base stations have a large cell coverage. In the hierarchical cell structure, a cell with a small coverage (referred to as a lower layer cell) overlaps with a cell with a large coverage (referred to as an overlay cell) (in whole or in part). In the example of FIG. 4, the macro / micro BS 41 is an overlay BS that serves a large cell 46, and the pico / femto BSs 42 and 43 are lower layer BSs that serve small cells 47 and 48. In addition, BS42 has a short distance A and is very close to BS41, and BS43 has a long distance B and is away from BS11. The mobile station MS44 is a pico / femto MS served by a pico / femto BS43, and the mobile station MS45 is a macro / microMS served by a macro / micro BS41. The MS45 is close to the Pico / Femto BS43 and is a long distance C away from its serving BS41.

  According to one novel aspect, a two-step uplink synchronization process is performed between the MS 44 and the BS 43. During the first step, the BS 43 encodes uplink (UL) transmission timing advance offset information and broadcasts the timing advance offset information to the MS 44. The MS 44 decodes the UL transmission timing advance offset information, and adjusts the UL transmission timing of the distance measurement or reference code based on the decoded timing advance offset value. During the second step, MS 44 performs normal uplink synchronization and accesses BS 43. As shown in the prior art, the two-step uplink synchronization process enables the use of ranging or reference codes with normal cyclic prefix (CP) length used for uplink synchronization and access, In addition, signals from the pico / femto BS 43 and the overlay macro / micro BS 41 are prevented from interfering with each other.

  As shown in FIG. 4, a mobile station (e.g., MS 44) served by a pico / femto cell is coupled to a memory 51, a processor 52, an information decoding module 53, an uplink access and timing adjustment module 54, and an antenna 56. Including transceiver 55. Similarly, a pico / femto base station (eg, BS 43) includes a memory 61, a processor 62, an information encoding module 63, a signal detection and timing estimation module 64, and a transceiver 65 coupled to an antenna 66. In one or more examples, the functions described in the two-stage UL synchronization process are implemented by different modules in hardware, software, firmware, or a combination thereof. The above-described functions can be realized in alignment with the same module, or can be realized by independent modules. Details of the two-stage UL synchronization process are described below with reference to the figures.

  For example, in a wireless communication system defined by the IEEE 802.16m standard, a base station and a mobile station communicate with each other by transmitting and receiving data mounted in a series of subframes. Before the mobile station accesses the base station, physical (PHY) layer synchronization and medium access control (MAC) layer random access are performed. When the power is turned on, the mobile station first acquires downlink (DL) synchronization through a synchronization channel (SCH) broadcast by the serving base station, and adjusts its timing, frequency, and power. After DL synchronization, the mobile station acquires uplink (UL) PHY layer synchronization through a ranging process, and acquires MAC layer random access through a network entry process with a serving base station. When a pico / femto cell is deployed in a hierarchical cell structure (e.g., radio system 40) with a macro / micro cell, DL and UL network timing synchronization is maintained and a pico / femto BS (e.g., BS 43) is maintained. Radio signals from overlay macro / micro BSs (eg, BS 41) need not interfere with each other when transmitted in the air.

  FIG. 5 is a diagram illustrating downlink, uplink subframes and transmission timing of a hierarchical cell structure (eg, wireless system 40) according to one novel aspect. In a time division duplex (TDD) system, a DL subframe is followed by a UL subframe, with a predetermined transmission switching gap (TTG) time between them. A DL subframe follows the UL subframe, and has a predetermined reception switching gap (RTG) time between the two. TTG and RTG are reserved to avoid possible collisions between downlink and uplink transmissions. In the example of FIG. 5, the macro / micro base station BS41 transmits data in the DL subframe period, receives data in the UL subframe period, and the pico / femto mobile station MS45 receives data in the DL subframe period. Data is transmitted in the UL subframe period. The MS 45 is located away from the serving BS 41, and the radio signal propagation time between the BS 41 and the MS 45 is referred to as a DL propagation delay. After DL and UL synchronization, the DL transmission timing of MS45 is synchronized with BS 41 having DL propagation delay, and the UL transmission timing of MS45 is synchronized with BS 41 having UL timing advance. For UL transmission, the UL timing advance associated with the absolute UL timing of BS41 is equal to the DL propagation delay.

  For pico / femto base station BS43, its cell coverage overlaps with overlay macro / micro base station BS41, so network timing synchronization simply means absolute timing synchronization between BS43 and BS41 is not. Under the same channel arrangement situation, BS43 and BS41 operate with the same frequency bandwidth, and network timing synchronization means timing synchronization of radio signals from BS43 and BS41 in the air. More specifically, since BS43 is located away from BS41 and close to MS45, the radio signal of a mobile station served by BS43 (e.g., MS44) is the radio signal of an adjacent mobile station served by BS41 (e.g., MS45). Prone to interfering with signals. For DL transmission, reception of MS45 from BS41 may be interfered by adjacent BS43 transmitting a signal to MS44. On the other hand, for UL transmission, reception of BS 43 from MS 44 may cause interference by transmitting signals to BS 41 from adjacent MS 45. As a result, network timing synchronization in the radio system 40 requires that DL and UL transmission timings between the pico / femto BS43 and its adjacent macro / micro MS45 are synchronized with each other to avoid interference. Means.

  As shown in FIG. 5, in order to synchronize BS 43 and MS 45, the predetermined TTG time and RTG time must be adjusted. For example, the UL transmission timing of the UL (RX) of the subframe 57 of the BS 43 (for example, indicated by a solid line) is determined based on the adjusted TTG time. In general, the TTG adjustment value is equal to the round trip time of the radio signal between BS43 and BS41, so uplink reception in BS43 UL (RX) subframe 57 is the UL (TX) of adjacent MS45 served by BS41. There is no interference with the uplink transmission in subframe 58.

  On the other hand, when the pico / femto BS 43 and the overlay macro / micro BS 41 operate with different frequency bandwidths, such TTG adjustment is not necessary particularly in a situation where the different frequency bandwidths are separated from each other. For example, as shown in FIG. 5, the UL transmission timing of the same UL (RX) subframe 57 of BS 43 (eg, indicated by a dotted line) is determined based on the original predetermined TTG time. Whether the TTG adjustment is necessary under such an arrangement situation is determined by the pico / femto base station.

  As a result, due to the downlink and uplink network timing synchronization request to the pico / femto base station, a predetermined TTG that is reserved to avoid collision between the downlink and uplink transmissions is transmitted to the pico / femto base station. It needs to be adjusted based on the location. However, there is no mechanism for knowing whether TTG coordination is applied in a pico / femto cell for a mobile station that camps on a pico / femto cell or camps on a pico / femto cell. This adjustment value cannot be known, and the understanding of the uplink transmission timing between the mobile station and the pico / femto BS is different.

  FIG. 6 is a diagram illustrating the downlink, uplink subframe, and transmission timing during initial ranging in the pico / femto cell. In the example of FIG. 6, the femto BS1 is arranged with the overlay macro BS in the same channel arrangement. For a macro BS, a UL subframe follows the DL subframe, and there is a predetermined TTG between them. A DL subframe follows the UL subframe, and there is a predetermined RTG between the two. In order to prevent the signals from the femto BS1 and the macro BS from interfering with each other, the femto BS1 applies a predetermined TTG having a TTG adjustment value. The TTG adjustment value is equal to the round-trip time of the radio signal between the femto BS1 and the macro BS. Subsequently, the femto BS1 adjusts the UL transmission timing used for the UL frame based on the adjusted TTG. Assume that mobile station MS1 is turned on within the cell coverage of femto BS1. MS1 does not know that the TTG adjustment value is applied to the femtocell by femtoBS1. Since MS1 does not know the TTG adjustment, MS1 uses the same predetermined TTG for its UL transmission timing. As a result, the UL transmission timing of MS1 has a timing difference compared to the UL transmission timing of femto BS1. This timing difference is equal to the TTG adjustment value.

  When MS1 performs initial ranging with femto BS1, if the cyclic prefix (RCP) length of the ranging channel is smaller than the timing difference, the introduced timing difference is femto BS1 and the ranging preamble signal Incomplete reception occurs. As shown in FIG. 6, according to one novel aspect, if femto BS1 informs MS1 of its TTG adjustment before initial ranging, MS1 is based on the same adjusted TTG value as femto BS1. The own UL transmission timing can be adjusted. Therefore, MS1 and femto BS1 can smoothly perform ranging after the UL synchronization process.

  FIG. 7 is a diagram showing a downlink, an uplink subframe, and transmission timing in a handover ranging period in a pico / femto cell. In the example of FIG. 7, the femto BS2 is arranged with the overlay macro BS, but the two BSs operate with different frequency bandwidths. For a macro BS, a UL subframe follows the DL subframe, and there is a predetermined TTG between them. A DL subframe follows the UL subframe, and there is a predetermined RTG between the two. Since femto BS2 operates with a different frequency bandwidth than overlay macro BS, it uses the same predetermined TTG and RTG for its DL and UL transmission timing and decides not to apply TTG adjustment. Assume that an adjacent mobile station MS2 is handed over from a macro BS to a femto BS2. MS2 is initially served by the macro BS, and its UL transmission timing is adjusted with timing advance, corresponding to the round trip time of the radio signal between the macro BS and MS2. MS2 does not know that a given TTG is applied in a femtocell by femto BS2. As a result, the UL transmission timing of MS2 has a timing difference compared to the UL transmission timing of femto BS2. Prior to handover, this timing difference is equal to the timing advance applied by MS2.

  When MS2 starts to perform handover ranging with femto BS2, if the length of ranging channel cyclic prefix (RCP) is smaller than the timing difference, the introduced timing difference is femto BS2 and the ranging preamble signal Incomplete reception occurs. As shown in FIG. 7, according to one novel aspect, if the femto BS2 announces its TTG adjustment value to the MS2 before handover ranging, the MS2 is based on the same TTG adjustment value as the femto BS2. The own UL transmission timing can be adjusted. Therefore, MS2 and femto BS2 can smoothly perform distance measurement after the UL synchronization process.

  In addition to the problem of incomplete reception of ranging preamble signals, non-pointing uplink transmission of ranging preamble signals also causes significant interference to other mobile stations served by the femto BS. For example, if the protection time of the ranging channel is less than the timing difference, the reception of uplink data from another MS in femto BS1 or femto BS2 will be interfered by the transmission of ranging preamble signals from MS1 or MS2 .

  The use of an asynchronous ranging channel with a long RCP length and guard time can partly solve the ranging and interference problems, but because of the various problems of the prior art part, it is a unified synchronous measurement. A distance channel is the preferred solution. To enable the use of a unified synchronous ranging channel, according to one novel aspect, it provides a two-step uplink synchronization process, pico / femto BS and overlay macro / micro BS, ranging and uplink Performs synchronization well and does not generate interference with another mobile station.

  Before discussing the details of the two-stage UL synchronization process, it should be noted that the above example takes a TDD system as an example, but the same principle can be applied to a frequency division bidirectional (FDD) system. . In the TDD system, “TTG adjustment” is used. However, in the FDD system, it is replaced by the more general term “transmission timing advance offset”. It should be further noted that although the above example has been described using an IEEE 802.16m system, the same principles apply to 3GPP systems. In the IEEE 802.16m WiMAX system, the mobile station transmits a ranging signal through a ranging channel (RCH) and performs UL synchronization. However, in the 3GPP LTE / LTE-A system, the user equipment (UE) transmits a reference code through a random access channel (RACH) to request UL access. Thus, ranging signals or reference codes and ranging channels or random access channels are used alternately in the uplink synchronization and access process.

  FIG. 8 is a flowchart of a method for two-stage uplink synchronization according to one novel aspect. In the example of FIG. 8, a two-stage UL synchronization process is performed between the mobile station and the pico / femto base station, and the mobile station and the pico / femto base station are overlay macro / micro base stations in the IEEE 802.16m system. Placed together. On the MS side, the MS first scans the synchronization channel (SCH) preamble transmitted by the neighboring base station (step 81). Thereafter, in step 82, the MS establishes DL synchronization with the candidate cell (eg, pico / femto cell). During DL synchronization, the MS obtains primary subframe header (P-SFH) and secondary SFH (S-SFH) information. During step 83, the MS determines whether the candidate cell belongs to a picocell or femtocell cell type. If so, the MS obtains UL transmission timing advance offset information from the SFH and derives a UL transmission timing advance offset value from the offset information (step 84). Thereafter, the MS advances the UL transmission timing used for ranging signal transmission based on the derived timing advance offset value (step 85). In step 86, after adjusting the UL transmission timing, the MS starts to perform pico / femto BS and normal ranging and automatic adjustment. On the other hand, if not, the MS directly initiates normal ranging and automatic adjustment and builds UL synchronization with the pico / femto BS (step 86). During the normal ranging process, the MS automatically encodes and transmits the ranging signal, receives and decodes the drift timing difference message transmitted from the pico / femto BS, and automatically based on the decoded drift timing difference. Therefore, the UL transmission timing is adjusted, and the ranging signal is retransmitted at the adjusted UL transmission timing. Finally, during step 87, the MS receives confirmation from the pico / femto BS and uplink synchronization is complete.

  During step 91, on the pico / femto BS side, the pico / femto BS first determines a UL transmission timing advance offset value (eg, a TTG adjustment value in the TDD system). Thereafter, in step 92, the pico / femto BS encodes the timing advance offset value into UL transmission timing advance offset information and broadcasts the offset information through a broadcast channel (BCH). During step 93, the pico / femto BS broadcasts the ranging signal arrangement to the MS. During step 94, the pico / femto BS detects the ranging signal transmitted from the MS, and the ranging signal is transmitted at the advanced UL transmission timing based on the broadcast offset information. During step 95, the pico / femto BS estimates the drift timing difference from the detected ranging signal. During step 96, the pico / femto BS determines whether the uplink timing is synchronized. If so, the pico / femto BS transmits confirmation information to the MS to complete uplink synchronization (step 98). On the other hand, if not, the pico / femto BS transmits a drift timing difference message to the MS and requests the MS to retransmit the ranging signal (step 97). The pico / femto BS returns to step 94 and repeats steps 94-97 until the uplink timing is synchronized.

  The UL transmission timing advance offset information described above is broadcast by the pico / femto base station, and such information is also transmitted by the overlay macro / micro base station. When the UE performs neighbor cell measurement and sends the measurement result back to the serving base station, the serving base station determines the handover target, transmits UE handover command and some location information by dedicated signaling, and the information is UL A transmission timing advance offset is included. In the 3GPP standard, dedicated signaling is completed by radio resource control (RRC) messages. In the IEEE 802.16 standard, dedicated signaling is completed by MAC management messages.

In one example, UL transmission timing advance offset information includes an encoded numerical value, and the encoded numerical value indicates a UL transmission timing advanced offset value (for example, a round trip delay time from a pico / femto BS to an overlay macro / micro BS). The total number of k bits is used for offset value signaling, N _RTO is provided on the pico / femto BS side, the parameter used to calculate the number of samples T _RTO , and T _RTO is the MS pico / femto cell Among them, it is assumed that the parameter is applied on the MS side when the initial distance measurement or the hand-over distance measurement is performed, and advances the distance measurement signal transmission timing. Mathematically, N _RTO and T _RTO are given by:
N _RTO = min ([RTD / (Tg-2)], 2 ^k -1)
T _RTO = [N _RTO * (Tg-2) * Fs] (samples)

  Although the present invention is illustrated by the specific embodiments described above, it is for illustration purposes and the present invention is not limited thereto. For example, the two-stage UL synchronization method is mainly applied to OFDM / OFDMA systems, but this method can be applied to systems having problems shown in other prior art, such as macro / micro (TD -SCDMA) vs. Pico / Femto (3GPPLTE / LTE-A). In addition, UL transmission timing advance offset information is broadcast by pico / femto base stations, but such information can be overlaid macro / micro base stations or dedicated signaling and other centralized network elements, Alternatively, it is transmitted by broadcast signal transmission. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims (26)

A method,
In a cellular communication system, a mobile station receives uplink (UL) transmission timing advance offset information from a base station, and the mobile station overlaps with a different cell coverage provided by another overlay base station Steps located within the range,
Adjusting the UL transmission timing based on the received UL transmission timing advance offset information; and executing UL synchronization and UL access with the base station;
A method comprising the steps of:   The method according to claim 1, wherein the UL transmission timing is advanced and used for ranging signal transmission through a ranging channel (RCH).   The method of claim 1, wherein the UL transmission timing is advanced and used for reference code transmission over a random access channel (RACH).   The method according to claim 1, wherein the UL transmission timing advance offset information indicates a round-trip propagation time of a radio signal between the base station and the overlay base station.   The method of claim 1, wherein the UL transmission timing advance offset information includes a coded numerical value indicating a UL transmission timing advance offset value.   The method of claim 1, wherein the mobile station decodes the UL transmission timing advance offset information broadcast by the base station over a broadcast channel (BCH). A mobile station,
Receive uplink (UL) transmission timing advance offset information from a base station in a cellular communication system, and the mobile station is located in a cell coverage that overlaps with a different cell coverage provided by another overlay base station Transceiver,
An information decoding module that decodes the UL transmission timing advance offset information, derives a UL transmission timing advance offset value, and performs UL transmission timing adjustment; and the base station, and UL access that performs UL synchronization and UL access; Timing adjustment module,
A mobile station characterized by comprising:   The base station according to claim 7, wherein the UL transmission timing used for ranging signal transmission by a ranging channel (RCH) is advanced based on the offset value.   The base station according to claim 7, wherein the UL transmission timing used for reference code transmission by a random access channel (RACH) is advanced based on the offset value.   The base station according to claim 7, wherein the UL transmission timing advance offset information indicates a round-trip propagation time of a radio signal between the base station and the overlay base station.   The base station according to claim 7, wherein the UL transmission timing advance offset information includes a coded numerical value indicating a UL transmission timing advance offset value.   The base station according to claim 7, wherein the information decoding module decodes the UL transmission timing advance offset information broadcast by the base station by a broadcast channel (BCH). A method,
Determining an uplink (UL) transmission timing advance offset value by a base station in a cellular communication system, the base station having a different cell coverage that overlaps a cell coverage of an overlay base station;
The UL transmission timing advance offset value is encoded into UL transmission timing advance offset information, the information is broadcast by a broadcast channel, and an uplink signal is detected from a mobile station, and the UL during initial uplink transmission is detected. Transmitting the uplink signal at adjusted transmission timing based on transmission timing advance offset information or timing advance estimated from the base station during subsequent uplink transmission;
A method comprising the steps of:   When the base station and the overlay base station operate at the same frequency bandwidth or close to the frequency bandwidth, the base station adjusts UL transmission timing based on the UL transmission timing advance offset. The base station according to claim 13.   When the base station and the overlay base station operate with different frequency bandwidths, the base station uses a predetermined value for UL transmission timing, or sets UL transmission timing based on UL transmission timing advance offset. The base station according to claim 13, wherein the base station adjusts.   The base station according to claim 13, wherein the uplink signal is a ranging signal transmitted through a ranging channel (RCH).   The base station according to claim 13, wherein the uplink signal is a reference code transmitted by a random access channel (RACH).   The base station according to claim 13, wherein the UL transmission timing advance offset value is equal to a round-trip propagation time of a radio signal between the base station and the overlay base station.   The base station according to claim 13, wherein the UL transmission timing advance offset information includes a coded numerical value indicating the UL transmission timing advance offset value. A base station,
Information encoding module for encoding uplink (UL) transmission timing advance offset value into UL transmission timing advance offset information,
In a cellular communication system, the UL transmission timing advance offset information is broadcast over a broadcast channel, and the base station has an uplink from a transceiver having a different cell coverage that overlaps the cell coverage of the overlay base station, and a mobile station. Detecting a signal and estimating a drift timing difference, wherein the uplink signal is estimated from the UL transmission timing advance offset information during initial uplink transmission or from the base station during subsequent uplink transmission. Based on the signal detection and timing estimation module transmitted with the adjusted transmission timing,
A base station comprising:   When the base station and the overlay base station operate at the same frequency bandwidth or close to the frequency bandwidth, the base station adjusts UL transmission timing based on the UL transmission timing advance offset. The base station according to claim 20.   When the base station and the overlay base station operate with different frequency bandwidths, the base station uses a predetermined value for the UL transmission timing, or sets the UL transmission timing based on the UL transmission timing advance offset. The base station according to claim 20, wherein the base station adjusts.   The base station according to claim 20, wherein the uplink signal is a ranging signal transmitted by a ranging channel (RCH).   The base station of claim 20, wherein the uplink signal is a reference code transmitted by a random access channel (RACH).   The base station according to claim 20, wherein the UL transmission timing advance offset value is equal to a round-trip propagation time of a radio signal between the base station and the overlay base station.   The base station according to claim 20, wherein the UL transmission timing advance offset information includes a coded numerical value indicating the UL transmission timing advance offset value.

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