Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J13/00—Code division multiplex systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/707—Spread spectrum techniques using direct sequence modulation
  • H04B1/7073—Synchronisation aspects
  • H04B1/7075—Synchronisation aspects with code phase acquisition
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/707—Spread spectrum techniques using direct sequence modulation
  • H04B1/7097—Interference-related aspects
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
  • H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
  • H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
  • H04B2201/70706—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation with means for reducing the peak-to-average power ratio
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/04—Speed or phase control by synchronisation signals
  • H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W56/00—Synchronisation arrangements
  • H04W56/0055—Synchronisation arrangements determining timing error of reception due to propagation delay
  • H04W56/0065—Synchronisation arrangements determining timing error of reception due to propagation delay using measurement of signal travel time
  • H04W56/007—Open loop measurement
  • H04W56/0075—Open loop measurement based on arrival time vs. expected arrival time
  • H04W56/0085—Open loop measurement based on arrival time vs. expected arrival time detecting a given structure in the signal

Definitions

• the method includes combining the primary synchronization channel and the secondary synchronization channel to produce a synchronization channel.
• the step of rotating the primary synchronization channel in phase comprises rotating the primary synchronization channel before the combining step.
• the first embodiment rotates only the primary synchronization channel and not the secondary synchronization channel.
• the step of rotating the primary synchronization channel in phase comprises rotating the synchronization channel in phase.
• the second embodiment rotates both the primary and secondary synchronization channels after they have been combined.
• the synchronization channel is combined with a dedicated channel to produce a downlink channel that is then rotated in phase.
• the present invention also includes an apparatus for performing the method summarized above.
• the apparatus includes a primary synchronization channel generator for generating a primary synchronization channel having the primary synchronization code; a phase rotator, coupled to the primary synchronization channel generator, for rotating the primary synchronization channel in phase according to a phase rotation sequence; and a transmitter, coupled to the phase rotator, for transmitting the primary synchronization channel.
• the apparatus further comprises a first combiner for combining the primary synchronization channel and the secondary synchronization channel to produce a synchronization channel; wherein the phase rotator is coupled between an output of the primary synchronization channel generator and an input of the first combiner.
• the phase rotator is coupled to an output of the first combiner.
• a second combiner combines the synchronization channel and a dedicated channel to produce a downlink channel, and the phase rotator is coupled to an output of the second combiner.
• FIG. 1 is a timing diagram illustrating the structure of the synchronization channel (SCH) of a W-CDMA system
• FIG. 2 is a functional block diagram of the multiplexing of the synchronization channel (SCH) with the other downlink physical channels (dedicated channels);
• FIG. 3 is a functional block diagram of a first embodiment of the present invention.
• FIG. 4 is a functional block diagram of a second embodiment of the present invention.
• FIG. 5 is a functional block diagram of a third embodiment of the present invention.
• FIG. 6 is a flow diagram of the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• FIGS. 1 and 2 The present invention will now be described in detail with reference to the exemplary W-CDMA system illustrated by FIGS. 1 and 2. It will be understood by one of ordinary skill in the art that the present invention is equally applicable to other communication systems in which fading is caused by destructive interference arising from the same synchronization or pilot channel being transmitted by more than one base station in the same geographic region.
• FIG. 3 a functional block diagram of a first embodiment of the present invention is illustrated.
• FIG. 3 is similar to FIG. 2, with the addition of phase rotator 302 between complex spreader 208 and combiner 214.
• Phase rotator 302 introduces a phase rotation of the primary SCH, after spreading with the primary synchronization code, c , and before combination with the secondary SCH.
• the signals illustrated in FIG. 3 as traveling between functional blocks are, in general, complex I and Q signals.
• the phase shift introduced by phase rotator 302 is pseudorandomly chosen for each slot from among a set of predefined phase shifts.
• a suggested set of predefined phase shifts would include zero, ⁇ /2, ⁇ , and 3 ⁇ /2 radians.
• Other predefined sets may be used in various embodiments.
• the present invention is not limited by the amount of the phase shift(s) chosen.
• phase rotator 302 generates the pseudorandom phase shift sequence, as well as introducing that phase shift into the primary SCH.
• the pseudorandom phase shift sequence may be provided to phase rotator 302 by a separate functional element.
• one convenient source of a pseudorandom number for controlling the phase shift introduced by phase rotator 302 is the secondary synchronization code, c s , generated by secondary code generator 212.
• the secondary synchronization code is not common to all base stations, but only to those of the same code group, it may be advantageously used to ensure that two base stations of different code groups having a phase collision of the primary SCH will not introduce the same pseudorandom sequence of phase shifts into their primary SCH, thereby prolonging the duration of the mutual interference.
• the secondary SCH is a binary data stream of logical ones and zeros, if the first chip were a "one” it could cause phase rotator 302 to introduce a phase shift of ⁇ radians into the primary SCH, whereas a "zero" could cause phase rotator 302 to introduce no phase shift into the primary SCH.
• the secondary SCH could be taken two chips at a time, with the '00' sequence corresponding to a zero phase shift, the '01' sequence corresponding to a phase shift of ⁇ /2 radians, the '10' sequence corresponding to a phase shift of ⁇ radians, and the '11' sequence corresponding to a phase shift of 3 ⁇ /2 radians.
• many different implementation schemes or pseudorandom sequences may be used, whether or not they are related to the secondary synchronization code.
• Phase rotator 302 preferably changes the phase of the primary SCH only once per burst transmission, which equates to once per slot.
• each repetition of the primary SCH would have a pseudorandom phase shift.
• the first slot of a frame might transmit the primary SCH with a phase shift of ⁇ radians
• the second slot of the same frame might transmit the primary SCH with a phase shift of zero radians.
• phase rotator 302 may change the phase of the primary SCH once per frame, rather than once per slot.
• each repetition of the primary SCH during a first frame would have a first pseudorandom phase shift
• each repetition of the primary SCH during a second frame would have a second pseudorandom phase shift, where the first and second pseudorandom phase shifts are not necessarily equal.
• many different timing schemes for pseudorandomly changing the phase of the primary SCH may be used, whether or not they are based on a slot or frame periodicity.
• phase rotator 302 of FIG. 3 introduces a pseudorandom phase shift in the primary SCH, after spreading by the primary synchronization code, and before combination with the secondary SCH.
• This pseudorandom phase shift mitigates the problem of phase collisions between multiple base stations, operating asynchronously, which all share the same primary synchronization code.
• FIG. 4 differs from FIG. 3 in that the phase rotation introduced by phase rotator 402 of FIG. 4 occurs after the combination of the primary SCH and the secondary SCH by combiner 214, rather than before their combination.
• rotator 402 may be similar in construction and functionality to phase rotator 302 of FIG. 3.
• phase rotator 502 introduces phase variations into the combined downlink (base station to mobile station) channel.
• phase rotator 502 is similar in operation and functionality to phase rotator 302 and phase rotator 402.
• the synchronization channel and the dedicated data channel are combined in combiner 216 prior to the introduction of phase rotation by phase rotator 502.
• the pilot symbols that are transmitted at the beginning of every slot of the dedicated data channel will be rotated in phase from slot to slot or frame to frame.
• a typical coherent demodulator (not shown) in the mobile station will generally accumulate pilot phase and energy over several consecutive slots in order to generate a stable channel estimate for coherently demodulating the data.
• the pseudorandom phase shift sequence introduced by phase rotator 502 may be based, as described above with reference to FIG. 3, on the secondary synchronization code, c s , contained in secondary code generator 212.
• the secondary synchronization code, c s is provided in the W-CDMA standard and is used by the mobile station in the second stage of the acquisition process. It is well known to the mobile station once it has demodulated the secondary SCH, and before it begins to demodulate the dedicated channels.
• the embodiment of FIG. 5 may be advantageously used to avoid the difficulties associated with pilot phase accumulation by the mobile station.
• the mobile station apply a phase rotation the received signal that is opposite of the one introduced by phase rotator 502 according to the secondary synchronization code before accumulation of the pilot phase.
• any method suggested above of encoding phase variations from the secondary synchronization code may be used (i.e., '0' is zero rotation, 'V is a rotation of ⁇ ), and any timing method suggested above may be used (i.e., once per slot, once per frame, etc.).
• FIG. 6 illustrates a flow diagram of the method of the present invention.
• the method described in FIG. 6 generically may be performed by any of the embodiments of FIGS. 3, 4, or 5.
• the primary synchronization channel is generated. This may be performed, for example, by spreading the output of ones generator 202 with the primary synchronization code signal generated by primary code generator 206 in complex spreader 208.
• the phase of the primary synchronization channel is rotated according to a phase rotation sequence. This step may be performed, for example, by any of phase rotator 302, phase rotator 402, or phase rotator 502. It should be noted that in the embodiment of FIG. 3, the phase rotator 302 acts on the primary SCH alone, whereas in the embodiments of FIGS.
• the phase rotators 402 and 502 respectively operate on a combination signal which inherently includes the primary SCH.
• the phase rotation sequence may be any recurring sequence sufficient to prevent prolonged fading due to destructive interference.
• the phase rotation sequence may be pseudorandomly shifting between zero and ⁇ radians every slot.
• Other example phase rotation sequences are given above.
• the primary synchronization channel is transmitted. This step may be performed by any conventional transmitter (not shown) within a base station that uses the present invention.
• a base station in a W-CDMA system will be able to avoid prolonged "fading" of the downlink signal caused by timing collisions on the primary SCH.
• the phase of the primary SCH By changing the phase of the primary SCH, the destructive interference that would otherwise occur in some regions in the mutual geographic coverage area of two base stations will be mitigated.
• the method of the present invention as implemented by the various embodiments described herein, will enable a mobile station to more rapidly acquire the downlink of the base station in such mutual interference situations.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Radio Transmission System (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=23279608

Family Applications (1)

Country Status (10)

Cited By (3)

Families Citing this family (81)

Citations (1)

Family Cites Families (5)

• 1999
  • 1999-06-08 US US09/328,119 patent/US6385264B1/en not_active Expired - Lifetime
• 2000
  • 2000-06-07 AU AU54682/00A patent/AU5468200A/en not_active Abandoned
  • 2000-06-07 WO PCT/US2000/015619 patent/WO2000076080A1/en not_active Ceased
  • 2000-06-07 BR BR0011414-6A patent/BR0011414A/pt not_active IP Right Cessation
  • 2000-06-07 AT AT00939622T patent/ATE308164T1/de not_active IP Right Cessation
  • 2000-06-07 DE DE60023497T patent/DE60023497T2/de not_active Expired - Lifetime
  • 2000-06-07 CN CNB008086893A patent/CN1152480C/zh not_active Expired - Fee Related
  • 2000-06-07 JP JP2001502242A patent/JP2003501936A/ja active Pending
  • 2000-06-07 EP EP00939622A patent/EP1190497B1/en not_active Expired - Lifetime
  • 2000-06-07 KR KR1020017015829A patent/KR100748402B1/ko not_active Expired - Fee Related

Patent Citations (1)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events