Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0868—Hybrid systems, i.e. switching and combining
  • H04B7/0871—Hybrid systems, i.e. switching and combining using different reception schemes, at least one of them being a diversity reception scheme
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/02—Terminal devices
  • H04W88/06—Terminal devices adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/12—Frequency diversity
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/0005—Control or signalling for completing the hand-off
  • H04W36/0055—Transmission or use of information for re-establishing the radio link
  • H04W36/0069—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink
  • H04W36/00692—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/10—Polarisation diversity; Directional diversity

Definitions

• the present invention relates to inter-frequency methods performed in or between wireless cellular systems and/or personal communications systems (PCS), wherein a mobile station while communicating with a base station over an RF link at a current operating frequency is required to tune to another operating frequency.
• PCS personal communications systems
• One such method has the purpose to accomplish a handover of the communication with the mobile station to an RF link at the new operating frequency to which the mobile station tunes, termed herein an "inter-frequency handover”.
• Another such method has the purpose of allowing the mobile station to measure signal quality at a set of candidate frequencies different than the current operating frequency, termed herein "inter-frequency signal quality measurement”.
• the latter method provides information for handover decisions.
• the present invention also relates to the structure of a mobile station as it relates to performance of inter-frequency methods.
• a method for performing an inter-frequency handover is known from A. Baier et al., "MULTI-RATE DS-CDMA RADIO INTERFACE FOR THIRD-GENERATION CELLULAR SYSTEMS", Seventh IEE European Conference on Mobile and Personal Communications, 13-15 December, 1993, pp. 255-260.
• Handovers are employed in wireless cellular systems and in PCS to allow mobile stations to travel from the coverage area of one base station to another while maintaining a call. While handovers are usually employed to transfer an ongoing communication with the mobile station from a current to a new base station, it is also possible to hand over a communication with the mobile station from one RF link to another of the same base station.
• a handover of a mobile station between base stations can be either a soft handover, in which during a transient period the mobile station simultaneously maintains communications with both the current and new base stations at the same frequency and receives the same data via both base stations, and a hard handover, where the mobile station switches from current links to new links generally at a new frequency and/or of a new network without such a transient period in which current and new RF links are simultaneously maintained.
• CDMA Code Division Multiple Access
• One method of improving the reliability of an inter-frequency handover is to use a transient compressed mode in which the data transmitted to the current base station at the current frequency FI is squeezed into the first halves of frames by doubling the instantaneous symbol rate RINF O while allowing the mobile station to tune to and establish communication at the new frequency F2 in the second halves of frames. While the compressed mode allows for a more gradual inter-frequency handover similar to a soft handover, there may be a deterioration of the bit error (BER) during the time that this mode is employed due to the doubling of the instantaneous symbol rate.
• BER bit error
• the structure or functionality with which a mobile station is provided to participate in or perform the aforementioned inter- frequency methods can also be used to improve the reliability and/or quality of its communications when the inter-frequency methods are not being participated in or performed by the mobile station.
• the present invention is based on the insight that providing the mobile station with two independently tunable transceivers, rather than the usual one transceiver, enables the mobile station to participate in an inter-frequency soft handover without a compressed mode and/or perform an inter-frequency signal quality measurement without a slotted mode, and when the two transceivers, which are coupled to respective antennas which antennas are spaced apart in distance, orientation or polarization, are tuned to the same operating frequency, the communications to and from the mobile station can be improved by the antenna diversity effect.
• a mobile station so equipped is configured for steering a mobile station side of an inter-frequency method wherein just prior to the commencement of the method, both transceivers are tuned to the same current operating frequency and are in communication with a current base station of the system, and at an intermediate stage in the method, one of the transceivers is tuned to another operating frequency while the other transceiver remains in communication with the current base station at the current operating frequency.
• the present invention also pertains to a stored program for a mobile station for steering the aforementioned method and to a method of operation of a mobile station.
• the inter-frequency method When the inter-frequency method is a soft handover, during the intermediate stage the one of the transceivers which is tuned to another operating frequency, referred to herein as a new operating frequency, establishes an RF link for communication at the new operating frequency, and after the intermediate stage the other transceiver is tuned to the new operating frequency.
• the inter-frequency method is a soft handover, during the intermediate stage the one of the transceivers which is tuned to another operating frequency is used to make a signal quality measurement, and after the intermediate stage this one of the transceivers is tuned back to the current operating frequency.
• both transceiver are tuned to the same frequency, and the antenna diversity effect is exploited.
• One method of exploiting the antenna diversity effect is by combining the baseband signals received from each transceiver and by linking the baseband signals to be transmitted by each transceiver.
• Figure 1 schematically shows a mobile station, which is arranged with two transceivers in accordance with the present invention, in conjunction with a pair of wireless cellular networks, each having a respective local base station with which the transceivers of the mobile station can communicate;
• Figures 2A, 2B, and 2C show the mobile station, and local base stations of Figure 1 and respectively generally depict the communication links with the mobile station just prior to, during, and just after an inter-frequency soft handover performed in accordance with the present invention
• Figures 3 A, 3B, and 3C show the mobile station, and local base stations of
• Figure 1 respectively generally depict the communication links with the mobile station just prior to, during, and just after an inter-frequency signal quality measurement performed in accordance with the present invention
• Figure 4 depicts the communications to and from the mobile station over the time interval spanning from just prior to to just after the inter-frequency soft handover, wherein time intervals A, B, and C generally correspond to the link depictions shown in Figures 2A, 2B, and 2C, respectively;
• FIG. 5 is a general schematic showing the structure of a mobile station in accordance with the present invention, including first and second identical but independently controllable RF sections; and
• Figure 6 is a schematic of one of the identical RF sections of Figure 5.
• DS-CDMA Direct Sequence Code Division Multiple Access
• PCS network of the type (e.g. CDMA 2000) that utilizes plural operating frequencies, such that there could be a handover requiring a mobile station to change from one operating frequency to another.
• Inter-frequency handovers may also be required in other wireless cellular or PCS systems utilizing more than one radio channel, and the principles of the present invention are equally applicable thereto.
• AMPS Analog Mobile Phone System
• TDMA Time Division Multiple Access
• GSM Global System for Mobile Communications
• JPDC Personal Communication Device
• UMTS Universal Mobile Telephone System
• an inter-frequency soft handover capable wireless cellular or PCS mobile station 10 which has a first antenna 12 coupled to a first transceiver 14 and a second antenna 13 coupled to a second transceiver 15.
• Transceivers 14 and 15 are tunable and are operable independently of each other with respect to transmission and reception. Further, antennas 12 and 13 are sufficiently spaced apart in distance and/or orientation or polarization in a manner that, when desired, one of transceivers 14 and 15 can be receiving RF while the other is transmitting RF at a different operating frequency.
• the spacing and relative orientation or polarization of the antennas 12 and 13 is also sufficient that an antenna diversity effect occurs when the transceivers 14 and 15 are tuned to the same frequency and transmit or receive the same signals.
• This antenna diversity effect is exploited by a diversity exploitation means 16.
• One mode of operation thereof is to combine the baseband signals received from transceivers 14 and 15, and to link the baseband signals supplied to transceivers 14 and 15 for transmission. For example the received baseband signals would be added together and the same baseband signals would be supplied to each transceiver for transmission.
• Another mode of operation of diversity exploitation means 16 is to use only the strongest received signal from transceivers 14 and 15 and supply a baseband signal to only the transceiver from which the strongest signal has been received.
• Mobile station 10 also includes an inter-frequency method steering means 17, with part 17a for steering a soft handover and part 17b for steering an inter-frequency signal quality measurement. The operation of the inter-frequency method steering means 17 will become more apparent as the discussion proceeds.
• Mobile station 10 is capable of roaming, including while on a call, from the wireless coverage area of a first base station 22 of a Direct Sequence Code Division Multiple Access (DS-CDMA) network 20 to the wireless coverage of a second base station 32, which may be of the same network, or of a different DS-CDMA different network 30 as illustrated, such that an "inter-frequency" handover is required.
• DS-CDMA Direct Sequence Code Division Multiple Access
• the call must be switched or transferred from a bi-directional link LI of mobile station 10 with local base station 22 of network 20, which is at an operating frequency FI, to a bi-directional link L2 of mobile station 10 with local base station 32 of network 30, which is at an operating frequency F2.
• transceivers 14 and 15 are independently operable at either frequency FI or F2, such that each could independently operate over link LI or link L2.
• FIGs 2A through 2C the course of events in an inter-frequency handover is more apparent from Figures 2A through 2C.
• FIG 2A just prior to an inter-frequency handover both transceivers 14 and 15 are operating over link LI at frequency FI to the current local base station 22, taking advantage of the antenna diversity effect e.g. by adding the signals received by both transceivers 14 and 18 or using only the one signal having the better signal quality.
• transceiver 15 is tuned to frequency F2 and begins to operate over link L2 to the new local base station 32.
• transceiver 14 is also switched to frequency F2, yielding the position shown in Figure 3C, wherein both transceivers 14 and 15 are operating over link L2 at frequency F2 to the new local base station 32, taking advantage of the antenna diversity effect.
• both transceivers 14 and 15 are operating over link L2 at frequency F2 to the new local base station 32, taking advantage of the antenna diversity effect.
• mobile station 10 prior to receiving a handover command from local base station 22 specifying base station 32 as the recipient of the handover, it is necessary for mobile station 10 to make inter-frequency signal quality measurements, e.g. of pilot strength, at other candidate operating frequencies, including F2, and send this information to the current base station 22.
• transceivers 14 and 15 eliminates the need for a slotted mode wherein idle slots appear sandwiched between leading and trailing active frame portions or partial frames, and the mobile station makes signal quality measurements during the slots. Idle slots, and the attendant increase of instantaneous symbol rate in the leading and trailing frame portions, are not needed. Inter-frequency signal quality measurements can be made using one of the transceivers, e.g. transceiver 15, to tune to the candidate frequency and measure pilot strength while the other transceiver, e.g. transceiver 14, remains in communication with the current base station at the current operating frequency.
• transceivers 14 and 15 are operating over link LI at frequency FI to the current local base station 22, taking advantage of the antenna diversity effect e.g. e.g. by adding the signals received by both transceivers 14 and 15 or using only the one signal having the better signal quality.
• transceiver 15 is tuned to frequency F2 and measures the strength of the pilot received at that frequency from base station 32, as an indication of signal quality.
• transceiver 15 is switched back to frequency FI, yielding the position shown in Figure 3C, wherein both transceivers 14 and 15 are again operating over link LI at frequency FI to the current local base station 22, taking advantage of the antenna diversity effect.
• the networks 20 and 30 appear conventional.
• the network 20 is shown as comprising two base stations 22, 24, a base station controller 26 which controls the plurality of base stations 22, 24, and a network controller 28 which controls network 20.
• network 30 is shown as comprising two base stations 32, 34, a base station controller 36 which controls the plurality of base stations 32, 34, and a network controller 38 which controls network 20.
• the network controllers are coupled by a communication link 40, and also each network controller is coupled to the public switched telephone network (PSTN) 42.
• PSTN public switched telephone network
• Figure 4 depicts communications in more detail between mobile station 10 and local base stations 22 and 32, wherein BS1 corresponds to base station 22 and BS2 corresponds to base station 32.
• BS1 corresponds to base station 22
• BS2 corresponds to base station 32.
• transceiver 15 switches its operating frequency to F2 and sends requests for acknowledgement RACH to the new base station 32, which ultimately replies with a signal Info, after which transceiver 18 sends an uplink signal Handover_Com to the new base station 32 that the handover is complete.
• transceiver 14 has remained in communication with current base station 22 and has continued to receive and send data, e.g.
• transceiver 14 tunes to frequency F2
• the transceiver 15 receives a seventh downlink data frame DL_Data_7.
• Baseband section 50 includes a digital signal processor (DSP) 50a, a microprocessor 50b, a non-volatile memory or ROM 50c, at least a portion of which is programmable, in which is stored firmware constituting programs and data for operation of DSP 50a and microprocessor 50b, including for steering the mobile station side of an inter-frequency soft handover, and inter-frequency signal quality measurements preceding the handover, and a volatile random access memory for temporary storage, primarily of data.
• DSP digital signal processor
• microprocessor 50b a non-volatile memory or ROM 50c, at least a portion of which is programmable, in which is stored firmware constituting programs and data for operation of DSP 50a and microprocessor 50b, including for steering the mobile station side of an inter-frequency soft handover, and inter-frequency signal quality measurements preceding the handover, and a volatile random access memory for temporary storage, primarily of data.
• Received and demodulated signals R are supplied from RF sections 42 and 46 to baseband section 50 via analog-to-digital converters 50e and 50f, respectively and DSP 50a performs despreading and decoding operations on the demodulated signals respectively, in a well known manner by application of the relevant pseudo noise (PN) code sequence, at the relevant phase.
• PN pseudo noise
• spread spectrum encoded signals T produced by DSP 50a are supplied to first RF section 42 and second RF section 46 via digital-to-analog converters 50g and 50h respectively in order to be modulated on a carrier and transmitted.
• command signals C such as tuning commands, are supplied from baseband section 50 to first RF section 42 and second RF section 46 via digital-to- analog converters 50i and 50j, respectively.
• Mobile station 10 further comprises in communication with baseband section 50, a numeric keypad 51, and a driver 52 for a display 53, e.g. an LCD screen, a microphone 54 and speaker 55.
• Microphone 54 communicates with baseband section 50 via an analog-to- digital converter 50k and baseband section 50 communicates with speaker 55 via digital-to- analog converter 501.
• the RF section comprises a diplexer 60 coupled to the applicable antenna 12 or 13, which receives from the output of a power amplifier 62 an RF spread spectrum communication signal to be transmitted by the antenna and supplies an RF spread spectrum communication signal to the input of a low noise amplifier 64 which has been received by the antenna.
• a modulator 66 preferably having a zero IF structure (not shown), receives a baseband spread spectrum communication signal from baseband section 50, and an RF carrier signal from voltage controlled oscillator or frequency synthesizer 68 and supplies an RF spread spectrum communication signal to the input of power amplifier 64.
• a demodulator 67 receives an RF spread spectrum communication signal from the output of low noise amplifier 64 and an RF carrier signal from oscillator or synthesizer 68 and supplies the baseband spread spectrum communication signal R to baseband section 50.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Radio Transmission System (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)
• Transceivers (AREA)

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• 2000
  • 2000-12-08 WO PCT/EP2000/012381 patent/WO2001047126A2/en not_active Application Discontinuation
  • 2000-12-08 CN CN00806535A patent/CN1372727A/zh active Pending
  • 2000-12-08 KR KR1020017010589A patent/KR20010102279A/ko not_active Application Discontinuation
  • 2000-12-08 JP JP2001547748A patent/JP2003518801A/ja not_active Withdrawn
  • 2000-12-08 EP EP00987369A patent/EP1219046A2/de not_active Withdrawn

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