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A new method of meandered variable pitch angle printed Quadrifilar Helix Antenna (MVPQHA) is described. This type of antenna helps in reducing the size of the printed quadrifilar helix antenna (PQHA) and makes the bandwidth of the antenna broader. The new type of antenna is compared with other existing types of printed quadrifilar helix antenna in terms of size, return loss and bandwidth

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A reservation based Medium Access Control (MAC) protocol has been adopted by the IEEE 802.16 standard as the basic protocol for data communication within the upstream channel. This standard adopts the binary exponential backoff algorithm with adjustable window size to resolve the collisions of request packets. This paper investigates the uplink access performance in terms of average throughput, average delay and collision probability for fixed number of contention slots, data slots and MAP size. The performance studies are made as a function of Request Backoff Start (RBS).

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