An efficient local predictive method for distributed timeslot allocation in CDMA/TDD

Abstract

Abstract-Slot allocation in a CDMA/TDD cellular network, which decomposes a frame into uplink and downlink slots, is a multi-dimensional optimization problem involving all the cells in the system due to interference between cells. However, the complexity of the problem makes it computationally too expensive to solve simultaneously for all the cells in a system of reasonable size. In this paper, we propose a novel predictive and distributed slot allocation scheme for transporting multimedia traffic over CDMA/TDD cellular networks with multiple cells, designed to maximize a general utility function that is (strictly) concave increasing. We formulate the utility-maximizing slot allocation problem as a nonlinear integer programming problem, and provide a solution that can be realized efficiently in a distributed manner. Also, we derive sufficient conditions for a real-number solution to be optimal and develop an efficient algorithm to find a near-optimal integer solution. The effectiveness of the integer solution is demonstrated by showing that its gap with the optimal solution is small. We show by experiments that the proposed predictive method has a sufficient accuracy when there are many active users in cells. Extensive simulation results show that the proposed distributed slot allocation method performs very well in comparison to an existing method.

Interference-Adaptive Fast Dynamic Channel Allocation in TD-SCDMA System

“…The slow DCA algorithm dynamically allocates resource units to a cell-related priority and preference lists, based on negotiation and measurements between adjacent cells, which classify the time slots so as to avoid the inter-cell interference, used as input to fast DCA [6]. As more advanced approaches to DCA, multi-dimensional optimization frameworks and solution have been proposed to show that dynamic resource allocation (DRA) can effectively handle the asymmetric traffic load over the UL and DL, while warranting the required signal-to-interference ratio (SIR) [8,9]. Since the above global optimization problem must be solved for joint slot allocations in all cells, it turns out to a large size non-linear integer programming problem, which is more complex than an NP-complete Knapsack problem [9].…”

“…As more advanced approaches to DCA, multi-dimensional optimization frameworks and solution have been proposed to show that dynamic resource allocation (DRA) can effectively handle the asymmetric traffic load over the UL and DL, while warranting the required signal-to-interference ratio (SIR) [8,9]. Since the above global optimization problem must be solved for joint slot allocations in all cells, it turns out to a large size non-linear integer programming problem, which is more complex than an NP-complete Knapsack problem [9]. Therefore, those approaches may not be practically feasible for implementation.…”

“…In TD-SCDMA system, dynamic channel allocation (DCA) is one of the most critical technologies that govern the overall capacity and service quality [4][5][6][7][8][9][10]. It can play an essential role in managing the various types of inter-cell interference, including the cross-time slot (CTS) interference that is a unique aspect in TDD systems.…”