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Wireless Personal Communications: Bluetooth and Other Technologies / Edition 1 available in Hardcover
Wireless Personal Communications: Bluetooth Tutorial and Other Technologies presents a broad range of topics in wireless communications, including perspectives from both industry and academia. The book serves as a reflection of emerging technologies in wireless communications and features papers from world-renowned authors on the subject.
A new tutorial on the emerging Bluetooth technology is also presented.
Wireless Personal Communications: Bluetooth Tutorial and Other Technologies serves as an excellent reference and may be used as a text for advanced courses on the subject. It is an essential tool for graduate students, postgraduate researchers, academics, and anyone working in the research aspect of the wireless communications industry.
|Series:||The Springer International Series in Engineering and Computer Science , #592|
|Product dimensions:||6.14(w) x 9.21(h) x 0.03(d)|
Read an Excerpt
Part III: Network System Design
B. Modeling of Diferent Fading CharacteristicsAn important new aspect of our simulation environment is the clear distinction between different fading characteristics. We consider an interference-limited system, where the influence of short-term fading is included in the statistical properties of the physical channel. Hence, for each target carrier-to-interference-ratio (C/I), we can set up a corresponding stochastic description of the erasure process. To take into account the long-term variations in the received signal, we can dynamically switch our model parameters with respect to measured C/1-profiles during a simulation run. Thus, the movement of a mobile terminal through a natural environment can be analyzed.
V. GSM General Packet Radio Service (GPRS)Against the background of the growth of both Internet and cellular phone users there is an evident need for an efficient wireless access to packet switched data networks. Current so-called 2nd generation mobile communication systems, e.g. GSM, are not able to serve this purpose. They have been designed on base of a circuit switched radio transmission for narrow band speech communications. This results in two major drawbacks for data transmission. Firstly, the available bandwidth per user is much too small to allow higher data rates and, secondly, data traffic in packet switched networks, e.g. the Internet, is bursty by nature. Conveying bursty traffic over a circuit switched bearer results in a highly ineffcient utilization of the available radio channels and causes unreasonable high costs for the user. Therefore, the Special Mobile Group (SMG) within the ETSIstandardization body launched in GSM phase 2+ the development of an efficient cellular packet data service. At the end of 1998, ETSI specified GPRS as a new bearer service for GSM networks to improve and simplify wireless access to packet data networks. It is build atop of the regular GSM protocol stack to facilitate a low complex and easy integration into already established GSM systems.
In the following, we will give a brief overview of the extended system architecture of a GSM GPRS system, where we will solely focus on the air interface, i.e. we will not consider session setup and tear down or the delivery and routing of packets between mobile stations and external packet data networks (e.g the Internet). Our descriptions are mainly based on .
A. The GPRS Protocol Stack
The basic idea behind the development of the GPRS specification was to ensure the concurrent existence of current voice transfer with future high-rate packet data transfer in common GSM networks. Thus, the GPRS protocol can be considered as a set of extensions of the existing GSM protocol stack. One important extension is related to channel allocation. In GRPS, a mobile station (MS) may use multiple time slots of the same TDMA frame. The channel allocation is very fast and flexible. The base station subsystem (BSS) assigns the available resources to the mobile stations according to a so-called capacity-on-demand principle, i.e. multiple users in a cell share a common physical channel. The allocation of the time slots may differ from TDMA frame to TDMA frame. This enables the system to allocate a channel only when either the mobile station or the BBS needs to send data packets. Moreover, downlink and uplink channels are assigned independently (asymmetric transmission). Hence, for bursty traffic this results in a very efficient usage of the valuable resource bandwidth.
The GPRS protocol stack can be gathered from Fig. 5. On top of the network layer, any packet data protocol can be applied. Most usually this will be the IP Protocol.
The Subnetwork Dependent Convergence Protocol (SNDCP) adapts the upper layer protocols to the functionality of the underlying GRPS layers. It performs segmentation and reassembly of long user data packets and provides means for header compression and data encryption on the mobile link to ensure privacy of user communication.
The data link layer encompasses three sublayers. Logical Link Control (LLC) is used to establish a logical link between MS and BBS and is based on LAPD, which is also part of the common GSM protocol stack. It supports point-to-point as well as point-to-multipoint connections. Backward error protection is provided in form of a Go-back-N retransmission protocol. The Radio Link Control (RLC) layer performs segmentation of the LLC packet data units (PDUs) into short blocks of fixed length according to one of the channel coding schemes described in subsection V-B. A block check sequence is appended (in dependence on the applied coding scheme this is either a Fire code or a CRC code), which allows in combination with sequence numbering the detection of erroneous or lost packets. In addition, RLC provides an optional Automatic Request (ARQ) protocol to achieve a reliable data transfer when needed. The Medium Access Control (MAC) sublayer performs multiplexing of user data and signaling information....