Điện thoại di động giao thức viễn thông cho các mạng dữ liệu P4

Wireless protocolsA MAC protocol for a wireless LAN provides two types of data-transfer Service Access Points (SAP): network and native. The network SAP offers an access to a legacy network protocol (e.g., IP). The native SAP provides an extended service interface that may be used by custom network protocols or user applications capable of fully exploiting the protocol specific Quality of Service (QoS) parameters within the cell service area. Broadband Radio Access Integrated Network (BRAIN) is used for millimeter wave band multimedia communications....
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Điện thoại di động giao thức viễn thông cho các mạng dữ liệu P4 Mobile Telecommunications Protocols For Data Networks. Anna Ha´ c Copyright 2003 John Wiley & Sons, Ltd. ISBN: 0-470-85056-6 4 Wireless protocolsA MAC protocol for a wireless LAN provides two types of data-transfer Service AccessPoints (SAP): network and native. The network SAP offers an access to a legacy networkprotocol (e.g., IP). The native SAP provides an extended service interface that may beused by custom network protocols or user applications capable of fully exploiting theprotocol specific Quality of Service (QoS) parameters within the cell service area. Broadband Radio Access Integrated Network (BRAIN) is used for millimeter waveband multimedia communications. In BRAIN, all Access Points (APs) need to have onlyan optical/electrical (OE) converter because BRAIN incorporates radio on fiber technolo-gies, which allow for transmitting radio signals through optical fiber cables. The Hybrid and Adaptive MAC (HAMAC) protocol integrates fixed assignment TimeDivision Multiple Access (TDMA) protocols, reservation-based protocols, and contention-based protocols into a wireless network, simultaneously and efficiently supporting variousclasses of traffic such as Constant Bit Rate (CBR), Variable Bit Rate (VBR), and Avail-able Bit Rate (ABR) traffic. The HAMAC protocol uses a preservation slot technique tominimize the packet contention overhead in Packet Reservation Multiple Access (PRMA)protocols, while retaining most isochronous service features of TDMA protocols to servevoice and CBR traffic streams. Adaptive Request Channel Multiple Access (ARCMA) is a Demand Assignment Multi-ple Access (DAMA) protocol with dynamic bandwidth allocation. This scheme is designedto function in a cell-based wireless network with many Mobile Stations (MSs) commu-nicating with the Base Station (BS) of their particular cell. Transmissions are done ona slot-by-slot basis without any frames. Each slot is divided into a Transmission Access(TA) slot and a Request Access (RA) minislot. The RA channel in ARCMA is capableof carrying additional information for different classes of Asynchronous Transfer Mode(ATM) service (e.g., CBR, VBR, etc.). This additional information is used by the BS toprovide better QoS support for different classes of traffic. Transmission from CBR trafficmay reserve an incremental series of slots in the duration of their transmission. No furtherrequest is needed until the CBR transmission finishes.56 WIRELESS PROTOCOLS4.1 WIRELESS PROTOCOL REQUIREMENTSThe general requirements for wireless protocols supporting wireless LANs are as follows:• The low cost is achieved by simple implementation and the use of standard multipurpose modules and components. Modularity and reconfigurability in all stages of system design are the key elements to meet these requirements.• The QoS requirements for the data-transfer service of the MAC protocol include support for user-defined traffic types and connection parameters. The protocol must support real-time data-transfer services.• The wireless LAN can be used both as an extension and as an alternative to a wired LAN. Therefore, for interoperability requirements, the changing topology of a wire- less network, inadequate security and reliability of the medium, and protocol-specific management functionality must be hidden from the network user, that is, from legacy Transmission Control Protocol/Internet Protocol (TCP/IP) applications.• Wireless medium does not provide the same level of confidentiality and user identifica- tion as a wired system. A wireless coverage area cannot be reliably defined or restricted. Actions at the MAC layer have to be taken to provide a secure data-transfer service.• An unlicensed and globally available frequency band must be selected for the system.• The architecture of the MAC protocol should follow a master–slave hierarchy as the centralized control and management enables an easy and efficient support of QoS parameters and an access point for outside network resources.• To guarantee the low cost, efficient resource management and guaranteed QoS, the number of simultaneous users in a single wireless LAN cell can be restricted according to the target environment.• The requirement for low power consumption follows from the usage of battery powered portable network equipment, for example, laptops. A wireless network adapter shoul ...