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Mobile users continue to demand higher data rates. With the continued growth in cellular services, laptop computer use and the Internet, wireless network providers are beginning to pay an increasing amount of attention to packet data networks. Enhanced Global Packet Radio Service (EGPRS) offers a substantial improvement in performance and capacity over existing GPRS services, in return for a relatively minimal additional investment. EGPRS, commonly called EDGE, achieves these enhancements to the GPRS system primarily by implementing changes to the Physical layer and to the Medium Access Control/Radio Link Control (MAC/RLC) layer. The significant improvements are a new modulation technique, additional modulation coding schemes, a combined Link Adaptation and Incremental Redundancy technique, re-segmentation of erroneously received packets, and a larger transmission window size.

Technical Differences Between GPRS And EGPRS


Regarded as a subsystem within the GSM standard, GPRS has introduced packet-switched data into GSM networks. Many new protocols and new nodes have been introduced to make this possible.

EDGE is a method to increase the data rates on the radio link for GSM. Basically, EDGE only introduces a new modulation technique and new channel coding that can be used to transmit both packet-switched and circuit-switched voice and data services. EDGE is therefore an add-on to GPRS and cannot work alone. GPRS has a greater impact on the GSM system than EDGE has. By adding the new modulation and coding to GPRS and by making adjustments to the radio link protocols, EGPRS offers significantly higher throughput and capacity.

Measurement Accuracy

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As in the GSM environment, GPRS measures the radio environment by analyzing the channel for carrier strength, bit error rate, etc. Performing these measurements takes time for a mobile station, which is of no concern in the speech world as the same coding is used all the time. In a packet-switched environment, it is essential to analyze the radio link quickly in order to adapt the coding toward the new environment. The channel analysis procedure that is used for GPRS makes the selection of the right coding scheme difficult since measurements for interference are performed only during idle bursts. As a result, measurements can only be performed twice during a 240-millisecond period.

For EGPRS, the standard does not rely on the same "slow" measurement mechanism. Measurements are taken on each and every burst within the equalizer of the terminal, resulting in an estimate of the bit error probability (BEP). Estimated for every burst, the BEP is a reflection of the current C/I, the time dispersion of the signal and the velocity of the terminal. The variation of the BEP value over several bursts will also provide additional information regarding velocity and frequency hopping. A very accurate estimation of the BEP is then possible to achieve.

Coding Schemes

For GPRS, four different coding schemes, designated CS1 through CS4, are defined. Each has different amounts of error-correcting coding that is optimized for different radio environments. For EGPRS, nine modulation coding schemes, designated MCS1 through MCS9, are introduced. These fulfill the same task as the GPRS coding schemes. The lower four EGPRS coding schemes (MSC1 to MSC4) use GMSK, whereas the upper five MSC5 to MSC9) use 8PSK modulation. Figure shows both GPRS and EGPRS coding schemes, along with their maximum throughputs.

EDGE Standard And References

The EDGE base station system work item provides a platform to employ new modulation techniques, whereas the EDGE network support subsystem work item defines the network changes to facilitate the physical layer. According to the work item descriptions, EDGE will provide two phases: Phase 1: Single- and multislot packet-switched services and single and multislot circuit switched services Phase 2: Real-time services employing the new modulation techniques that are not included in Phase 1.

Phase 1 has been completed with 3GPP Release 99. Phase 2 is ongoing in the 3GPP standardization, and its scope has been extended to cover the alignment with WCDMA and the provisioning of Internet protocol (IP) multimedia. This concept, currently standardized in 3GPP, is known as GERAN.

This paper has presented an overview of EDGE with particular focus on the physical layer and the data link layer. The goal of EDGE is to provide a packet data network that provides operating rates that are of adequate speed for most applications. EDGE achieves this increase in throughput rate mainly through enhancements to the physical layer and the RLC/MAC layer of the GPRS system.


Unknown said...

this topic is too good but i want more info on it possible to give the paper on it as i want it to give as a seminar

Unknown said...

this topic is too good but i want more info on it possible to give more info on this.thank you

Jilani said...


This topic is nice. But i need more information about this. So please send me the total topic as early as possible..thank you

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