The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform

Preben Mogensen - One of the best experts on this subject based on the ideXlab platform.

  • capacity gain of an uplink synchronous wcdma system under Channelization Code constraints
    IEEE Transactions on Vehicular Technology, 2004
    Co-Authors: J O Carnero, Klaus I Pedersen, Preben Mogensen
    Abstract:

    The performance of an uplink-synchronous wide-band Code-division multiple-access (WCDMA) system is evaluated for radio environments with low temporal dispersion. The capacity gain of synchronous WCDMA is evaluated theoretically under certain constraints and by means of extensive dynamic system level simulations for more advanced scenarios. The effect of Channelization Code shortage, the impact of the dispersive radio channel on the orthogonality of received signals, and soft handover are some of the considered effects. The potential capacity gain is found to equal 35.8% in a multicell scenario, conditioned on an infinite number of Channelization Codes per cell. For a more realistic scenario with Channelization Code constraints, the capacity gain is reduced to 9.6%. The absolute number of users per cell, relative to the available number of Channelization Codes within each scrambling Code group, is therefore found to be an important metric. This further suggests that the capacity gain of synchronous WCDMA decreases when other capacity-enhancing techniques are deployed, such as uplink antenna diversity, soft handover, voice activity detection, etc. The presented simulation results in the case where soft handover is not considered accurately match the analytical findings.

  • capacity gain of beamforming techniques in a wcdma system under Channelization Code constraints
    IEEE Transactions on Wireless Communications, 2004
    Co-Authors: J Ramiromoreno, Klaus I Pedersen, Preben Mogensen
    Abstract:

    This study addresses the performance of a wideband Code-division multiple-access mobile communications system with beamforming antenna arrays (AAs) at the base station, synthesizing a grid of beams. In order to fully exploit the capacity gain from beamforming without jeopardizing the stability of the system, a directional power-based admission control (AC) scheme is applied. Due to the higher capacity offered by beamforming techniques, shortage of orthogonal Channelization Codes in the downlink becomes an increasingly important factor, which may result in blocking of users before the interference power limit is reached. The problem of Channelization Code shortage is addressed, and a solution based on splitting the cell into several Code regions is proposed. For a network with circuit switched data services operated at 64 kb/s, the capacity gain for an eight-element AA is found to equal a factor of 2.5 for a universal mobile telecommunications equivalent system, with one Channelization Code set per cell. The capacity gain is limited by severe Channelization Code shortage under these circumstances. This problem is solved by deploying a cell splitting strategy with multiple Code regions, which subsequently results in a capacity gain increase to a factor of 3.4. Furthermore, the soft capacity mechanism associated with partial deployment of AAs in a subset of the cells in the network is also addressed. It is demonstrated that a hot spot cell with AAs also helps increase the capacity of the surrounding cells with conventional sector antennas when using a power-based AC strategy.

M. Sawahashi - One of the best experts on this subject based on the ideXlab platform.

  • variable spreading factor ofcdm with two dimensional spreading that prioritizes time domain spreading for forward link broadband wireless access
    IEICE Transactions on Communications, 2005
    Co-Authors: Noriyuki Maeda, Yoshihisa Kishiyama, Hiroyuki Atarashi, M. Sawahashi
    Abstract:

    This paper proposes the optimum design for adaptively controlling the spreading factor in Orthogonal Frequency and Code Division Multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional orthogonal Channelization Code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. We first demonstrate the reduction effect of inter-Code interference by the proposed two-dimensional orthogonal Channelization Code assignment. Then, computer simulation results show that in time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency of f D = 1500 Hz, becomes SF Time = 16. Furthermore, it should be decreased to SF Time = 8 for such a very fast fading environment using 16QAM data modulation. We also clarify when the channel load is light such as C mux /SF = 0.25 (C mux and SF denote the number of multiplexed Codes and total spreading factor, respectively), the required average received signal energy per symbol-to-noise power spectrum density ratio (E s /N 0 ) is reduced as the spreading factor in the frequency domain is increased up to say SF Freq = 32 for QPSK and 16QAM data modulation. When the channel load is close to full such as when C mux /SF = 0.94, the optimum spreading factor in the frequency domain is SF Freq = 1 for 16QAM data modulation and SF Freq = 1 to 8 for QPSK data modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hotspot cell configurations assuming various channel conditions.

  • variable spreading factor ofcdm with two dimensional spreading that prioritizes time domain spreading for forward link broadband wireless access
    Vehicular Technology Conference, 2003
    Co-Authors: Noriyuki Maeda, Yoshihisa Kishiyama, Hiroyuki Atarashi, M. Sawahashi
    Abstract:

    This paper proposes the optimum design for adaptively controlling the spreading factor in orthogonal frequency and Code division multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional Channelization Code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. Computer simulation results elucidate that bit-interleaving in the frequency domain is superior to chip-interleaving especially for a full channel load because bit-interleaving exhibits a large randomization effect of burst errors, while still maintaining Code orthogonality. In time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency f/sub D/ = 1500 Hz, becomes SF/sub Time/ = 16, and it should be decreased to SF/sub Time/ = 8 for such a very fast fading environment using 16QAM modulation. When the channel load is light such as C/sub mux//SF = 0.25 (C/sub mux/ and SF denote the number of multiplexed Codes and total spreading factor, respectively), the required average received signal energy per symbol-to-background noise power spectrum density ratio (E/sub s//N/sub 0/) is reduced as the spreading factor in the frequency domain is increased up to say SF/sub Freq/ = 32 for QPSK and 16QAM modulation, respectively (Note that, nevertheless, 16QAm modulation under such a lighter channel load condition is replaced by QPSK modulation together with two fold the channel load as 16QAM to achieve the same information bit rate). Meanwhile, when the channel load is close to full such as when C/sub mux//SF = 0.94, the optimum spreading factor in the frequency domain is SF/sub Freq/ = 1 for 16QAM modulation and SF/sub Freq/ = 1 to 8 for QPSK modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hot-spot cell configurations assuming various channel conditions.

Noriyuki Maeda - One of the best experts on this subject based on the ideXlab platform.

  • variable spreading factor ofcdm with two dimensional spreading that prioritizes time domain spreading for forward link broadband wireless access
    IEICE Transactions on Communications, 2005
    Co-Authors: Noriyuki Maeda, Yoshihisa Kishiyama, Hiroyuki Atarashi, M. Sawahashi
    Abstract:

    This paper proposes the optimum design for adaptively controlling the spreading factor in Orthogonal Frequency and Code Division Multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional orthogonal Channelization Code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. We first demonstrate the reduction effect of inter-Code interference by the proposed two-dimensional orthogonal Channelization Code assignment. Then, computer simulation results show that in time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency of f D = 1500 Hz, becomes SF Time = 16. Furthermore, it should be decreased to SF Time = 8 for such a very fast fading environment using 16QAM data modulation. We also clarify when the channel load is light such as C mux /SF = 0.25 (C mux and SF denote the number of multiplexed Codes and total spreading factor, respectively), the required average received signal energy per symbol-to-noise power spectrum density ratio (E s /N 0 ) is reduced as the spreading factor in the frequency domain is increased up to say SF Freq = 32 for QPSK and 16QAM data modulation. When the channel load is close to full such as when C mux /SF = 0.94, the optimum spreading factor in the frequency domain is SF Freq = 1 for 16QAM data modulation and SF Freq = 1 to 8 for QPSK data modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hotspot cell configurations assuming various channel conditions.

  • variable spreading factor ofcdm with two dimensional spreading that prioritizes time domain spreading for forward link broadband wireless access
    Vehicular Technology Conference, 2003
    Co-Authors: Noriyuki Maeda, Yoshihisa Kishiyama, Hiroyuki Atarashi, M. Sawahashi
    Abstract:

    This paper proposes the optimum design for adaptively controlling the spreading factor in orthogonal frequency and Code division multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional Channelization Code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. Computer simulation results elucidate that bit-interleaving in the frequency domain is superior to chip-interleaving especially for a full channel load because bit-interleaving exhibits a large randomization effect of burst errors, while still maintaining Code orthogonality. In time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency f/sub D/ = 1500 Hz, becomes SF/sub Time/ = 16, and it should be decreased to SF/sub Time/ = 8 for such a very fast fading environment using 16QAM modulation. When the channel load is light such as C/sub mux//SF = 0.25 (C/sub mux/ and SF denote the number of multiplexed Codes and total spreading factor, respectively), the required average received signal energy per symbol-to-background noise power spectrum density ratio (E/sub s//N/sub 0/) is reduced as the spreading factor in the frequency domain is increased up to say SF/sub Freq/ = 32 for QPSK and 16QAM modulation, respectively (Note that, nevertheless, 16QAm modulation under such a lighter channel load condition is replaced by QPSK modulation together with two fold the channel load as 16QAM to achieve the same information bit rate). Meanwhile, when the channel load is close to full such as when C/sub mux//SF = 0.94, the optimum spreading factor in the frequency domain is SF/sub Freq/ = 1 for 16QAM modulation and SF/sub Freq/ = 1 to 8 for QPSK modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hot-spot cell configurations assuming various channel conditions.

Klaus I Pedersen - One of the best experts on this subject based on the ideXlab platform.

  • capacity gain of an uplink synchronous wcdma system under Channelization Code constraints
    IEEE Transactions on Vehicular Technology, 2004
    Co-Authors: J O Carnero, Klaus I Pedersen, Preben Mogensen
    Abstract:

    The performance of an uplink-synchronous wide-band Code-division multiple-access (WCDMA) system is evaluated for radio environments with low temporal dispersion. The capacity gain of synchronous WCDMA is evaluated theoretically under certain constraints and by means of extensive dynamic system level simulations for more advanced scenarios. The effect of Channelization Code shortage, the impact of the dispersive radio channel on the orthogonality of received signals, and soft handover are some of the considered effects. The potential capacity gain is found to equal 35.8% in a multicell scenario, conditioned on an infinite number of Channelization Codes per cell. For a more realistic scenario with Channelization Code constraints, the capacity gain is reduced to 9.6%. The absolute number of users per cell, relative to the available number of Channelization Codes within each scrambling Code group, is therefore found to be an important metric. This further suggests that the capacity gain of synchronous WCDMA decreases when other capacity-enhancing techniques are deployed, such as uplink antenna diversity, soft handover, voice activity detection, etc. The presented simulation results in the case where soft handover is not considered accurately match the analytical findings.

  • capacity gain of beamforming techniques in a wcdma system under Channelization Code constraints
    IEEE Transactions on Wireless Communications, 2004
    Co-Authors: J Ramiromoreno, Klaus I Pedersen, Preben Mogensen
    Abstract:

    This study addresses the performance of a wideband Code-division multiple-access mobile communications system with beamforming antenna arrays (AAs) at the base station, synthesizing a grid of beams. In order to fully exploit the capacity gain from beamforming without jeopardizing the stability of the system, a directional power-based admission control (AC) scheme is applied. Due to the higher capacity offered by beamforming techniques, shortage of orthogonal Channelization Codes in the downlink becomes an increasingly important factor, which may result in blocking of users before the interference power limit is reached. The problem of Channelization Code shortage is addressed, and a solution based on splitting the cell into several Code regions is proposed. For a network with circuit switched data services operated at 64 kb/s, the capacity gain for an eight-element AA is found to equal a factor of 2.5 for a universal mobile telecommunications equivalent system, with one Channelization Code set per cell. The capacity gain is limited by severe Channelization Code shortage under these circumstances. This problem is solved by deploying a cell splitting strategy with multiple Code regions, which subsequently results in a capacity gain increase to a factor of 3.4. Furthermore, the soft capacity mechanism associated with partial deployment of AAs in a subset of the cells in the network is also addressed. It is demonstrated that a hot spot cell with AAs also helps increase the capacity of the surrounding cells with conventional sector antennas when using a power-based AC strategy.

J O Carnero - One of the best experts on this subject based on the ideXlab platform.

  • capacity gain of an uplink synchronous wcdma system under Channelization Code constraints
    IEEE Transactions on Vehicular Technology, 2004
    Co-Authors: J O Carnero, Klaus I Pedersen, Preben Mogensen
    Abstract:

    The performance of an uplink-synchronous wide-band Code-division multiple-access (WCDMA) system is evaluated for radio environments with low temporal dispersion. The capacity gain of synchronous WCDMA is evaluated theoretically under certain constraints and by means of extensive dynamic system level simulations for more advanced scenarios. The effect of Channelization Code shortage, the impact of the dispersive radio channel on the orthogonality of received signals, and soft handover are some of the considered effects. The potential capacity gain is found to equal 35.8% in a multicell scenario, conditioned on an infinite number of Channelization Codes per cell. For a more realistic scenario with Channelization Code constraints, the capacity gain is reduced to 9.6%. The absolute number of users per cell, relative to the available number of Channelization Codes within each scrambling Code group, is therefore found to be an important metric. This further suggests that the capacity gain of synchronous WCDMA decreases when other capacity-enhancing techniques are deployed, such as uplink antenna diversity, soft handover, voice activity detection, etc. The presented simulation results in the case where soft handover is not considered accurately match the analytical findings.