This paper proposes a measurement scheme of instantaneous signal-to-average interference plus background noise ratio (SIR) for SIR-based fast transmit power control (TPC) using time-multiplexed pilot symbols on the reverse link of DS-CDMA mobile radio. Both pilot and data are used for signal power measurement, but pilot symbols are used for measurement of average interference plus noise power. By the means of computer simulation, the TPC parameters, i. e. , SIR measurement period and step size, are optimized to maximize the link capacity in a Rayleigh fading environment. The capacity of the power controlled reverse link with channel coding and Rake combining is evaluated to understand the effects of the number of resolvable propagation paths, fading maximum Doppler frequency(or mobile traveling speed), and antenna diversity reception in single-cell and multi-cell environments.

Direct sequence code division multiple access (DS-CDMA) is a promising candidate for 3rd generation mobile communications systems. We recently proposed a coherent multicode DS-CDMA (CM-CDMA) scheme that uses pilot symbol-aided coherent RAKE, interference power measurement based transmit power control, orthogonal multicode transmission, and concatenated channel coding. We have implemented a CM-CDMA test-bed for a series of laboratory and field tests using the 2 GHz band. This paper describes the test-bed system and experimental results are presented. It is confirmed that pilot symbol-aided coherent RAKE can reduce the required signal energy per bit-to-interference plus background noise spectrum density ratio (Eb/Io) by 2-3 dB from that achievable with differential detection. Also shown is that by using both RAKE combining and SIR-based power control the transmit power of mobile stations can be significantly reduced. Measurement results show that the required Eb/Io degrades only slightly when 24 code-channels (768 kbps) are used since orthogonal Gold sequences are used as short spreading codes.

This paper analyzes performances of trellis coded(TC) 8PSK modulation in Rician fading channels to optimize parameters of Viterbi decoders. The computer simulation clarifies that when carrier power to multipath power ratio (C/M) equals 10dB, Pe performance with reasonable length interleaving depends on free Euclidean distance (dfree) but not on effective code length(ECL) in a practical range of bit error probability (Pe= 10-3-10-4). In the case of C/M=5dB, the effect of ECL appears in the range of bit energy to noise power density ratio (Eb/No)C/M (=5dB). Therefore, for domestic mobile satellite communication systems for non-high latitude countries, only dfree must be considered for TC8PSK Viterbi decoder design. Moreover, to improve Pe performance in slow fading environment, pre-Viterbi-decoding maximal ratio combining is proposed. The proposed diversity scheme improves required Eb/No to achieve Pe=10-4 by more than 6dB compared with no interleaving and more than 2.5 dB compared with interleaving.

Field experiments using the 2 GHz carrier frequency band were conducted nearby Tokyo to evaluate the effect of joint use of Rake combining and antenna diversity and also the effect of spreading chip rate (or bandwidth) on the achievable bit error rate (BER) performance and the mobile station transmit power distribution of power controlled coherent DS-CDMA reverse-link (mobile-to-base). Four chip rates, 0. 96, 1. 92, 3. 84, and 7. 68 Mcps, were used. The command interval and power step size of the fast transmission power control (TPC) used in the experiments, 1. 25 ms and 1 dB, respectively, were based on measurements of signal-to-interference plus background noise power ratio (SIR) after Rake combining. The field experiments demonstrate that the joint use of antenna diversity and Rake combining significantly improves the BER performance and, furthermore, that increasing the chip rate improves the BER performance and decreases the transmit power because of enhanced Rake combining through an increase in the number of resolved paths.

The reverse link performance of coherent multicode DS-CDMA [4], [5] under multipath Rayleigh fading environments is evaluated by computer simulation. It is demonstrated that the combined use of pilot symbol assisted (PSA)-coherent RAKE, channel coding, antenna diversity, and transmit power control is powerful in lowering the required signal energy per information bit-to-interference plus additive white Gaussian nose (AWGN) power spectrum density ratio (Eb/Io) which is an important parameter in determining the link capacity. It is also demonstrated that with slight performance degradation, high rate data transmission is realized by using multiple orthogonal spreading codes in parallel (orthogonal multicode transmission). Based on the simulated link performance, the reverse link cell capacity and link budget are also evaluated. It is found that parameter η=Io/No plays an important role in controlling the cell capacity and the maximum allowable path loss, where No is the AWGN power spectrum density.