Access and scheduling techniques in cellular systems in .NET Generate Code 128 Code Set A in .NET Access and scheduling techniques in cellular systems bar code for vb

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Access and scheduling techniques in cellular systems generate, create none none for none barcode ean 39 800 msec. The FRMA scheme is none none found to reach its maximum data rate of 18 kbps at a delay of less than 800 msec (Narasimhan and Yates, 1996). It is important to note, however, that a price is paid for these signi cant improvements in performance provided by the FRMA access procedure: the voice-packet dropping rate is always kept at about 1%, even when the system is lightly loaded.

This number is a constraint on, and, hence, built into the optimization procedure. PRMA has the 1% packet dropping rate as a threshold, i.e.

, the voice-packet dropping rate is less than or equal to 1%. A lightly loaded PRMA system would have a packet dropping rate of much less than 1%. The nal TDMA-based access scheme we discuss (many more have been proposed and studied in the literature!) is DQRUMA (Distributed Queueing Request Update Multiple Access), a multiple-access protocol designed principally for xed packet transmission over wireless local-area networks (LANs) (Karol et al.

, 1995a). (In another paper by the same authors, the work is extended to show how DQRUMA may be adapted to large cellsize systems (Karol et al., 1995b).

) This protocol attempts to provide more ef cient use of system capacity. Uplink frames carry multiple mini-slot request access (RA) channels plus the usual packet-length information slots. The mini-slot RA channels thus use less capacity than would be the case with full-slot contention channels.

Mobiles contend for access, transmitting a b-bit short mobile-access id, using one of the RA channels, selected randomly from those available. (The number of bits b used depends on the number of mobiles a base station can support.) The number of RA channels varies dynamically from frame to frame, depending on the number of mobiles requesting access.

With traf c light, the base station can allocate more RA channels in a frame, so announcing in a downlink message. The downlink frames, from base station to mobiles, carry acknowledgement channels, one for each RA-channel uplink. If access contention by a mobile, using one of the RA channels, is successful, the mobile recognizing its id, as transmitted downlink on the corresponding ACK channel, it transmits an information packet on the next slot uplink.

(This procedure thus applies to wireless LANs principally, for which the round-trip processing plus propagation delay is relatively small. As noted above, however, other work indicates how the DQRUMA protocol may be adapted to large cell-size systems (Karol et al., 1995b).

) If the mobile has additional information packets to transmit (its packet buffer is non-empty), it so signals with a one-bit piggyback request ag attached to its packet transmission. Subsequent packet accesses are thus collision-free. (A CDMA version of DQRUMA, to be described brie y below, incorporates a p-bit piggyback request eld, indicating the number of additional packets the mobile proposes to transmit.

This eld is incorporated as well in the initial access contention using the RA minislot.) A modi ed slotted-Aloha access procedure, mobiles using an adaptive access attempt probability, is suggested as the contention access procedure (Karol et al., 1995b).

Simulations indicate that this dynamic slotted-Aloha access technique as well as another proposed algorithm perform quite well, resulting in a packet delay vs throughput characteristic close to that of an ideal access scheme, in which the base station has complete, perfect information of all access requests each slot time. The piggyback request-bit procedure. Visual C# Karol, M. J. et al.

1995a. An ef cient demand-assignment multiple-access protocol for wireless packet (ATM) networks, Wireless Networks, 1, 5 (October), 267 279. Karol, M.

J. et al. 1995b.

Distributed-queueing request update multiple access (DQRUMA) for wireless packet (ATM) networks, IEEE International Conference on Communications, ICC 95, Seattle, WA, June, 1224 1231..
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