This paper proposes a mobile station (MS)-controlled fast MAC-layer handover (HO) scheme to reduce the HO latency in Mobile WiMAX. Based on the received signal strength (RSS) from any Base Station (BS), the MS can estimate its present distance from that BS. This capability allows the MS, through utilization of the broadcast messages by its Serving BS (SBS) and through few scannings of the Neighbouring BSs (NBS), to self-track its own direction of motion relative to the SBS and the NBSs and thus look ahead to perform an intelligent choice of the Target BS (TBS) for the impending HO. Simulation studies have shown a considerable reduction in the HO latency in the proposed method.

A novel approach toward realizing a large capacity high-throughput pipelined content addressable memory (CAM) or associative memory (AM) at low cost has been described. It employs only commercial random access memory (RAM) along with a simple binary search pipeline (BSPL). In order to search a (2/sup n/-1)-word search key field (SKF) storage RAM, the BSPL employs n identical and simple binary search processing elements, each having its local copy of the SKF storage RAM (SKFSR). The SKFSR stores, in an ordered manner, the SKFs of all the words in the CAM, whereas a data field storage RAM (DFSR) stores the unordered CAM data words. The n-times replicated SKFSR, along with the n-processor BSPL, functions as a simple n-stage pipelined content-to-address memory (CTAM). The CTAM, a new kind of memory that performs the inverse function of a RAM, serves as the first and the most important stage in the proposed 3-stage pipelined CAM architecture. In response to the stream of input query words (search keys) fed to the pipelined CAM, the pipelined CTAM first produces the corresponding stream of SKFSR addresses where the query words reside. These SKFSR addresses corresponding to the queries are next mapped back by the second stage, namely, the address mapping RAM, to their original addresses in the CAM, i.e., in the DFSR, which had been altered due to data ordering in the SKFSR. Now, the third stage of the pipelined CAM, namely, the DFSR, is read out at the mapped, i.e., the original CAM addresses, to obtain the desired stream of responses from the CAM. An augmented version of the pipelined CTAM has been designed to handle the presence of duplicate search keys in the CAM. A few illustrative examples of querying a simple database stored in the CAM have been included. The proposed pipelined CAM has a modular and highly scalable architecture. Its throughput rate, which is independent of the CAM size, is a little less than the RAM access rate and its latency is a little more than (n+2) times the RAM access time.

Implementation procedure of a known algorithm for direct conversion between signed magnitude and two's complement representation of signed binary numbers has been presented. In many situations, this direct conversion procedure is more desirable than the commonly used one via one's complement.

A new technique for generating a wide-band frequencymodulated sinusoidal carrier is presented. The frequency-modulated square-wave output of a voltage-controlled oscillator (VCO) is first filtered through a constant-Qswitched capacitor-type tracking bandpass filter (BPF) whose switched sinusoidal FM output is then passed through anRCtracking low-pass filter (LPF). The modulating signal itself is used to proportionally modulate the bias of a field effect transistor (FET), acting as the variable resistance in the LPF, so that a near perfect tracking is obtained. This ensures a very low-distortion frequency-modulated sinusoidal carrier at the output of the LPF. The conditions for ideal tracking have been presented, along with the description of an experimental circuit and test results.