30-06-2012, 05:35 PM
EDGE Compact and EDGE Classic Packet Data Performance
EDGE Compact ,EDGE Classic (1).doc (Size: 183.5 KB / Downloads: 30)
Abstract
Even though cellular radio services have been extremely successful in providing untethered voice communications, wireless data services have captured only a limited market share so far. One obstacle for wireless data services is their limited peak bit rates. Existing wireless data rates, up to several tens of kb/s, may be over one order of magnitude short of what is required to make popular applications user-friendly. To accomplish these necessities we go for EDGE(Enhanced Data Rates for GSM Evolution) employs adaptation between a number of modulation and coding schemes (“link adaptation”) as a means for providing several hundred kb/s peak rates in a macro-cellular environment while supporting adequate robustness for impaired channels. In this paper we discuss the two phases of EDGE, classic and compact. We start our discussion with the link adaptation and incremental tendency techniques. Secondly we go for discussing EDGE classic and compact systems and their deployment scenarios, followed by downlink performance comparison and some MAC layer enhancement techniques which improve the performance.
INTRODUCTION
The GSM system is the most popular second-generation wireless system today. It employs TDMA technology to support mobile users in different environments. This system, initially standardized and deployed in Europe, is currently deployed worldwide. The TDMA community adopted EDGE for high-speed data services in the third-generation, radio transmission technology proposal to ITU for IMT-2000 (“UWC-136”). Typically, current GSM service provider’s employ 3/9 or 4/12 reuse plans and they may not impose a different frequency reuse plan for EDGE, which is thus termed “EDGE Classic.” However, in North America, initial deployment using 1MHz in each direction is being considered due to limited spectrum and the potential need to re-deploy spectrum currently used for ANSI 136 systems. This implies very aggressive frequency reuse having a minimum of only three 200-kHz frequency carriers. This means allocating one frequency to each of the three sectors per base station and reusing the frequency set everywhere (“1/3 reuse”) and providing control signaling with extra reuse protection in the time domain, which is named “EDGE Compact” due to its compact spectrum requirement.
MODULATION AND CODING ADAPTATION
The basic concept of EDGE is to provide higher data rates per radio time slot than is possible with GMSK modulation. This allows the support of existing services with a lower number of time slots. In addition it allow s the introduction of new services with up to 59.2 kb/s per timeslot or almost 480 kb/s per carrier in multi-slot operation, hence offering an evolution path for GSM to support multimedia applications.
Radio link formats
Discussions in the ETSI workshops resulted in selection of 8PSK/GMSK to provide higher rates than the GMSK modulation with small envelope fluctuations and to provide backward compatibility to GSM and GPRS. The EDGE concept can be seen as an extension of GPRS for packet service, which is called EGPRS. ETSI has also combined EDGE with circuit switched data modes, and these modes are called ECSD.