"Battery life" and "cost" constraints are presenting new challenges for the design of wireless networks. The major focus of past research on transmit power control, diversity, modulation and coding techniques has been limited to maximizing coverage and/or capacity for cellular telephone systems. However, for battery powered wireless handsets connected through indoor wireless links, the optimization objective is shifting from link efficiency to battery efficiency and cost. In this thesis, the battery life of handsets and the cost of network are both addressed for an indoor code division multiple access (CDMA) communications system using time division duplex (TDD).
A wireless handset needs a large dynamic range transmitter amplifier in order to overcome channel path loss and fading. This makes the amplifier inefficient such that its power consumption becomes proportional to the peak transmit power. Therefore, the amplifier needs a large, heavy and expensive battery which lasts for only a few hours. Indoor wireless users, however, need small, light, low cost handsets with batteries that last for days rather than for a few hours.
To achieve a long battery life for handsets, a system architecture is proposed in which each cell uses a central base station along with several radioports. The radioports placed at optimal or near-optimal locations in order to minimize the maximum path loss experienced by handsets. Each radioport may use more than one antenna to combat Rayleigh fading. The central base station selects the radioport that provides the strongest maximally ratio combined signal. An infra-structure cost model is developed for the proposed system, which depends on the peak transmit power capability of handsets and of other system parameters and performances.
The number of parameters affecting the network infra-structure cost is high, which makes the cost minimization problematic. To avoid large computation time, a new network planning approach is proposed: its objective is to minimize the cost under the constraints of handset peak transmit power, outage probability, and call blocking probability. As well, the reverse link of the CDMA system is analyzed and a closed form equation for the outage probability of the link is derived, and computer simulations are used to verify it.
To reduce costs, transmit power control in the handsets is a necessity. In CDMA systems, all handsets use the same frequency bandwidth, which results producing mutual interference. An open loop power control algorithm is proposes and its performance addressed. Simulation results show that the proposed power control algorithm is successful under the conditions specified.
Optimal placement of the radioports can reduce the peak transmit power of handsets and/or the network cost. Two algorithms are proposed for the placement of radioports. The first is a modified version of the Sebestyen algorithm. The second is a hybrid of genetic and K-means algorithms. Simulation results show that the proposed hybrid algorithm can produce global or near global optimal solutions in most cases
