Congestion-based routing strategies in multihop TDD-CDMA networks

In this paper, a network topology is investigated that allows both peer-to-peer and nonlocal traffic in a cellular-based time-division duplex code-division multiple-access (TDD-CDMA) system known as opportunity driven multiple access (ODMA). The key to offering appropriate performance of peer-to-peer communication in such a system relies on the use of a routing algorithm which minimizes interference. This paper presents a study of the constraints and limitations on the capacity of such a system using a variety of routing techniques. A congestion-based routing algorithm is presented that attempts to minimize the overall power of the system as well as providing a measure of feasibility. This technique provides the lowest required transmit power in all circumstances, and the highest capacity in nearly all cases studied. All of the routing algorithms studied here allocate TDD time slots on a first come first served basis according to a set of predefined rules. This fact is utilized to enable the development of a combined routing and resource allocation algorithm for TDD-CDMA relaying. A novel method of time slot allocation according to relaying requirements is then developed. Two measures of assessing congestion are presented based on matrix norms. One is suitable for current interior point solution, the other is more elegant but is not currently suitable for efficient minimization and, thus, practical implementation.