Performance improvement techniques for channel-adaptive random access

Abstract

Channel-adaptive random access was proposed to reduce the transmission power required for random access in a Time-Division-Duplex (TDD)-based wireless system. With channel-adaptive random access, random access packet transmission is postponed until transmission condition is satisfied. Therefore, with channel-adaptive random access, it is possible to reduce the power consumption of random access compared to traditional random access. In this dissertation, two performance improvement techniques are investigated for channel-adaptive random access. First, efficient energy allocation is proposed between a preamble and message in a random access packet. The performance is evaluated for a random access packet considering the detection probability of a preamble as well as the error rate of message. To minimize the packet error probability with channel-adaptive random access, the optimum energy allocation is obtained between the preamble and the message. The performances with the optimum and sub-optimum energy allocations are compared by simulation. The results show that about 0.5 dB performance gain can be achieved with the optimum energy allocation compared to the sub-optimum energy allocation. Second, variable measurement interval is proposed for discontinuous channel measurement. After each channel measurement, the proposed next measurement interval is adaptively determined based on previous channel measurement. The performances with fixed and variable measurement intervals are compared by simulation. The results show that the receiver power consumption for channel measurement can be reduced with variable measurement interval under the same average transmission delay constraints compared with fixed measurement interval.