IEEE 802.16-2001 pdf download IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems
6.MAC common part sublayer (CPS)
A network that utilizes a shared medium requires a mechanism to efficiently share it. A two-waypoint-to-multipoint wireless network is a good example of a shared medium: here the medium is the spacethrough which the radio waves propagate.
The downlink, from the base station (BS) to the user, operates on a point-to-ultipoint basis. TheEEE Std 802.16-2001 wireless link operates with a central BS and a sectorized antenna which is capable ofhandling multiple independent sectors simultaneously. Within a given frequency channel and antenna sectorall stations receive the same transmission, or parts thereof, The base station is the only transmitter operatingin this direction, so it transmits without having to coordinate with other stations, except for the overall timedivision duplexing that may divide time into uplink and downlink transmission periods. It broadcasts to allstations in the sector (and frequency): stations check the address in the received messages and retain onlythose addressed to them.
In the other direction, the user stations share the uplink to the BS on a demand basis. Depending on the classof service utilized, the SS may be issued continuing rights to transmit, or the right to transmit may be grantedby the BS after receipt of a request from the user.
n addition to individually addressed messages, messages may also be sent on multicast connections (contromessages and video distribution are examples of multicast applications) as well as broadcast to all stations.
Within each sector, users adhere to a transmission protocol that controls contention between users andenables the service to be tailored to the delay and bandwidth requirements of each user application. This isaccomplished through five different types of uplink scheduling mechanisms. These are implemented usingunsolicited bandwidth grants, polling, and contention procedures. Mechanisms are defined in the protocol toallow vendors to optimize svstem performance using different combinations of these bandwidth allocationtechnigues while maintaining consistent inter-operability definitions. For example. contention may be usedto avoid the individual polling of SSs which have been inactive for a long period of time.
The use of polling simplifies the access operation and guarantees that applications receive service on a deterministic basis if it is required. In general, data applications are delay tolerant, but real-time applications like voice and video require service on a more uniform basis and sometimes on a very tightly-controlled schedule.
IEEE 802.16-2001 pdf download
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