RS-ISMA is a wireless access protocol designed for wireless multimedia communications and implemented in the BRAIN indoor-LAN prototype. In addition, a compact RF module composed of flat antennas and an MMIC was employed for each remote station and AP. The use of large capacity FPGA decreased the number of signal processing boards. System parameters such as the packet format were optimized for IP datagram transport to support all applications based on IP. The function of NACK sensing was added to RS-ISMA to ensure an efficient and smooth wireless multicast in a multiple-access environment.

The HAMAC protocol uses a super frame that is divided into two frames, the downlink frame and the uplink frame. The length of the frames can vary depending on the bandwidth demand. The downlink frame is used by the BS to broadcast the frame configuration information, the connection setup, the allocation information, the request information, and the data to all mobile devices. The information and the data can be broadcast using a single burst because only the BS controls the downlink. Mobile devices can filter out irrelevant information upon receiving them. The first segment of the downlink frame is used for control signaling needed for the frame configuration to be known by all mobile devices before starting the reception and the transmission.

ARCMA implements a dynamic RA channel in which an entire uplink channel can be converted into multiple RA channels. This conversion is done when the Request Table is empty, which in most cases indicates heavy collisions in the request channel. ARCMA uses an algorithm that takes advantage of the random access scheme in the RA channel. We use the slotted ALOHA with BEB as the random access protocol for ARCMA.

The request is made in the RA channel (RA minislot). The request data packet contains the mobile's b-bit Access ID assigned during setup. In ARCMA protocol, in addition to the Access ID, the request packet also includes the type of service being requested. The protocol provides additional support for periodic traffic (i.e., CBR). Since traffic can be either CBR or non-CBR, only a single bit is required to identify the service type. This bit is transmitted together with the request packet in the RA channel. DQRUMA provides no distinction between requests of different service types. The distinction provided in ARCMA is used by the BS to assign priority to CBR traffic.

0 0

Post a comment