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We consider efficient scheduling for a delay constrained CDMA Wireless Sensor Network (WSN). Given a twotiered WSN model, we first find the optimum schedule for the intra-cluster communications, that minimizes the total transmit power of the sensor nodes, while maintaining the short term average throughput at each sensor. We show that the specifics of the scheduling problem enables it polynomially solvable. Next, We consider the inter-cluster communications where cluster heads are capable of employing two antennas and use Alamouti scheme to achieve the transmit diversity (TD). We observe that our proposed scheduling protocol applied to the intercluster communications provides a near-optimum solution, with a modest sacrifice in performance and significant savings in computational complexity as compared to the optimum scheduler. Simulation results are presented to demonstrate the performance of the proposed scheduling protocols, and the considerable power savings they provide with respect to the TDMA-type scheduling.

Abstract-We consider efficient scheduling for a delay constrained multi-rate CDMA system. We first find the optimum schedule for CDMA systems without transmit diversity (TD), that minimizes the average transmission energy per bit while maintaining the short term average throughput for each user in the system. We observe that the specifics of the scheduling problem enables it polynomially solvable. Next, we consider the case when mobile devices are capable of employing two antennas and use Alamouti scheme to achieve TD. We observe that our proposed scheduling protocol can be extended to the system with TD with a modest sacrifice in performance and significant saving in computational complexity, as compared to the optimum scheduler. Simulation results are presented to demonstrate the performance of the proposed scheduling protocols, and the considerable energy savings they provide with respect to the TDMA-type scheduling.

Abstract-We consider the problem of adaptive cell sectorization in a CDMA system when the receiver employs a linear multiuser detector. Specifically, given the number of sectors and terminal locations, we investigate how to appropriately sectorize the cell, such that the total transmit power is minimized, while each user has acceptable quality of service, under the assumption that the base station employs linear multiuser detectors. The resulting joint optimization problem has high complexity for arbitrary signature sequences, so we concentrate on the tractable case where the square of the crosscorrelation values between the signature sequences are equal. We formulate the sectorization problem for different linear detectors. The optimum sectorization problem with linear multiuser detector has the same complexity as the one with the matched filter. Numerical results suggest that significant power saving is achieved by incorporating better receiver structures, i.e. MMSE detector, or decorrelator.

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