EDGE technology

CONTENTS

Mobile evolution Edge technology GPRS EDGE system performance Channel coding and frame structure Applications Conclusion

INTRODUCTION

In just a few years the Internet has transformed the way we access information, communication and entertainment services at home and at work. Broadband connections have made the Internet experience richer for millions of people and in the coming years, millions more will turn to wireless technology to deliver their broadband experience. This paper aims to cut through the confusion and hype surrounding the relative merits of various wireless broadband technologies and get to the real issues that will influence the mass-market success of mobile broadband and its ability to deliver broadband for all and everywhere. while there are a host of technologies competing to deliver commercial mobile broadband services the most recent being Mobile WiMAX 3G networks based on well established WCDMA (Wideband Code Division Multiple Access) and HSPA(High Speed Packet Access) technologies offer the best way forward in terms ofglobal efficiency. HSPA is the undisputed leader in mobile broadband services, as it provides: an ecosystem of unrivalled breadth and depth, covering both traditional mobile terminals and personal consumer devices such as notebooks, ultra mobile PCs, cameras, portable game consoles and music players acceptance, economies of scale and spectrum

unmatched economies of scale that benefit all players in the ecosystem, which are uniquely available to a technology that is part of the 3GPP family ofstandards, currently serving over two billion subscribers ever-improving performance, with commercially-proven transmission bit-rates of up to 14Mbps today and up to 42Mbps in the near future highly economic a urban and rural coverage, with up to 200km cell range and measured speeds in excess of 2Mbps at the cell border clearly defined and easily adopted evolution path. Mobile WiMAX does not offer any technology advantage over HSPA. HSPA low cost embedded modules are already available and with over 100 commercial networks in operation, HSPA is the clear and undisputed choice for mobile broadband services. Enhanced data for global evolution(EDGE) is a high speed mobile data standard,intended to enable second generation global system for mobile communication (GSM) and time division multiple access(TDMA). Transmits data at up to 384 kilobits per second(Kbps)Today, the Internet is a true global marketplace, where people can find the products and services they desire. It is also a global town square, where people can meet,chat and blog. It is a global library and information repository that is unprecedented inthe history of mankind. The Internet is our doctor, lawyer, banker, government official providing us with a direct channel to government authorities, health services and local communities. It is becoming the entertainment channel of choice; offering us anunparalleled selection of music, TV, video and news at our fingertips. The Internet will continue to develop as the place for information, communication,interaction and media consumption. However, to enjoy the complete benefits of the Internet, people need a broadband connection. As a consequence, Internet broadband connectivity has become one of the most widespread communications developments ever and the growth in demand for high-speed Internet connections is

set to continue. Today there are over 250 million broadband users: by 2012 this figure is forecast to grow to over 1.8 billion. Most people today experience broadband via a PC connected over a fixed line (usually DSL or cable). However, for many of the broadband users expected to get online over the next few years, a fixed line is simply not an option and wireless networks will be their primary broadband access method (as shown in Figure 1).

In 1st G AMPS(Advanced Mobile system) developed in U.S in 1983 In 2nd G there was introduction of CDMA,TDMA and GSM Between 2nd and 2.5th G of GPRS Between 2.5th and 3rd G there was an introduction EDGE TECHNOLOGY

THE STAGES OF EDGE

Network architectureThe IEEE 802.16 standardization only covers basic connectivity up to Media AccessControl (MAC) layer; the WiMAX Forum also addresses network architecture issues for WiMAX networks. Figure 6: Overview of WiMAX Forum Network Reference Architecture. The first WiMAX Forum network reference architecture specification (release 1.0) is focused on delivering a wireless Internet service, with mobility, as the first step (Figure 6). Release 1.5 will add support for telecom-grade mobile services, supporting full IMS interworking, carrier-grade VoIP, broadcast applications like mobile TV and over-the-air provisioning. In comparison 3GPP handles GSM and WCDMA standardization for a complete mobile system, including terminal aspects, radio access networks, core networks, and parts of the service network. 3GPP networks already support IMS-based services, carrier-grade voice, regulatory requirements like E911 and lawful intercept, broadcast applications like mobile TV and over-the-air provisioning for user terminals. The overall complexity of the different network architectures is very similar which is not surprising as the goal is to deliver the same functionality (as can be seen in Figure 7).

Mobile evolution

1st generation mobile communication 2nd generation mobile communication 2.5th generation mobile communication 3rd generation mobile communication

3G and above EDGE Technology Evolutionary path to 3G services for GSM and TDMA operators Builds on General Packet Radio Service (GPRS) interface and networks air

Phase 1 (Release99 & 2002 deployment) supports best effort packet data at speeds up to about 384 kbps Phase 2 (Release2000 & 2003 deployment) will add Voice over IP capability Enhanced Data rates for GSM Evolution

Coverage

HSPA is a Frequency Division Duplex (FDD) technology, in

which the uplink and downlink are in separate frequency channels (usually denoted as 2x5MHz). Mobile WiMAX is a Time Division Duplex (TDD) technology, in which there is just one frequency channel that is shared between the uplink and the downlink. The ratio between the uplink and the downlink defines how they share the frequency channel

in time. A 1:1 ratio indicates time split 50/50 between the uplink and the downlink as outlined

3GPP evolutionHSPA is at least four years ahead of other mobile broadband technologies. It supports the delivery of mobile broadband and fixed wireless broadband services in any of the mobile spectrum bands (850MHz, 900MHz, 1800MHz, 1900MHz, 2.1GHz and 2.6GHz) and during 2007 it is expected that at least five of these bands will carry commercial traffic. However, HSPA is only one step in the evolution of mobile broadband. Delivering peak rates of 14Mbps in the downlink and 5.8Mbps in the uplink today, its evolution adds support for MIMO and 64QAM that will deliver 42Mbps in the downlink and 11.5Mbps in the uplink. In parallel, LTE will deliver further enhancements in peak rates (exceeding 100Mbps), in addition to scalable channel bandwidths using OFDMA with both TDD and FDD operation. LTE and HSPA-evolved offer maximum spectrum flexibility while delivering true high-speed, high-quality 4G performance.

TechnologyEDGE/EGPRS is implemented as a bolt-on enhancement for 2G and 2.5G GSM and GPRS networks, making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade. Although EDGE requires no hardware or software changes to be made in GSM core networks, base stations must be modified. EDGE compatible transceiver units must be installed and the base station subsystem needs to be upgraded to support EDGE. New mobile terminal hardware and software is also required to decode/encode the new modulation and coding schemes and carry the higher user data rates to implement new services.

Transmission techniquesIn addition to Gaussian minimum-shift keying (GMSK), EDGE uses higher-order PSK/8 phase shift keying (8PSK) for the upper five of its nine modulation and coding schemes. EDGE produces a 3-bit word for every change in carrier phase. This effectively triples the gross data rate offered by GSM. EDGE, like GPRS, uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel, and thus the bit rate and robustness of data transmission. It introduces a new technology not found in GPRS, Incremental Redundancy, which, instead of retransmitting disturbed packets, sends more redundancy information to be combined in the receiver. This increases the probability of correct decoding.

EDGE can carry data speeds up to 236.8 kbit/s for 4 timeslots (theoretical maximum is 473.6 kbit/s for 8 timeslots) in packet mode and will therefore meet the International Telecommunications Union's requirement for a 3G network, and has been accepted by the ITU as part of the IMT-2000 family of 3G standards. It also enhances the circuit data mode called HSCSD, increasing the data rate of this service.

ClassificationWhether EDGE is 2G or 3G depends on implementation. While Class 3 and below EDGE devices clearly are not 3G, class 4 and above devices perform at a higher bandwidth than other technologies conventionally considered as 2G as 1xRTT). Because of the variability, EDGE is generally classified as 2.75G network technology.

GPRSGeneral Packet Radio Service (GPRS) is a packet oriented Mobile Data Service available to users of Global System for Mobile Communications (GSM) and IS-136 mobile phones. It provides data rates from 56 up to 114 kbps. GPRS can be used for services such as Wireless Application Protocol (WAP) access, Short Message Service (SMS), Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access. GPRS data transfer is typically charged per megabyte of throughput, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user

actually is utilizing the capacity or is in an idle state. GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain Quality of Service (QoS) is guaranteed during the connection for non-mobile users. 2G cellular systems combined with GPRS is often described as "2.5G", that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused Time division multiple access (TDMA) channels in, for example, the GSM system. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that GSM is the only kind of network where GPRS is in use. GPRS is integrated into GSM Release 97 and newer releases. It was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP).EDGE SYSTEM PERFORMANCE

Multiprotocol support Today the 2G base station backhaul networks use TDM while the 3G networks are based on the combination of TDM and packettechnology. As Ethernet transport becomes more widely available with the promise of cost savings, operators need a solution for merging the existing networks into Ethernet. The Tellabs 8600 system provides a solution that helps the operator to migrate the existing networks to packet technology costeffectively. The Tellabs 8600 system has all of the common TDM

(PDH, SDH, SONET) interfaces as well as Ethernet interfaces. TDM, ATM, Frame Relay and HDLC are forwarded using MPLS pseudowires, which can be carried over Ethernet, SDH or SONET network. This provides flexibility for choosing the optimal network technology for transport.

Moving from TDM to packet Packet networks provide an optimal solution for bursty dataservices. Packet switches save aggregate bandwidth by means of statistical multiplexing. This is based on an assumption that the average bandwidth of a connection is much less than the peak rate. The averaging of the bandwidth increases the queuing delay, especially if the bursts arrive at the same time from several sources. This is, however, usually accepted for data services. Voice and other TDM services require constant bandwidth and minimal delay and jitter over the network. This is achieved by assigning these services the highest priority. The Tellabs 8600 packet scheduling supports both the real-time and data services in the same network. Delay-critical services will be assigned highest priority to guarantee the best performance. At the same time, data

services can utilize statistical multiplexing witha high overbooking factor, which saves transmission bandwidth in

THE GSM EDGE SYSTEMIn the GSM EDGE system the transmitted data sequence is 8PSK modulated and passed through a Gaussian pulse shaping filter to adjust the signal to the GSM systems bandwidth. The pulse shaping filter causes Inter Symbol Interference (ISI) to the signal ranging 5 symbol periods However, the optimal To compensate for the ISI, an equalization (MLSE) The performance with is of efficient channel equalizer is needed in the GSM EDGE system. maximumlikelihoodsequence the mobile radio channel estimation conditions.

computationally too complex, due to the high level modulation and suboptimum equalizers are studied], where promising results are found in the class of reduced-state trellis-based equalizers: Delayed Decision-Feedback Sequence Estimation (DDFSE) and Reduced-State Sequence Estimation (RSSE), a generalization of DDFS. create a minimum-phase overall impulse response, should be used to trade performance for complexity. Another promising method for equalization, with low computational requirement and near optimal performance, is to use iterative optimization for the equalization process Channel coding is used in 8PSK EDGE to For achieve satisfactory bit error rate (BER) performance of the 8PSK EDGE schemes and possibly creation of new ones.

NFSK/LPSK the channel coding schemes will require modifications

IMPROVING THE GSM EDGE SYSTEM By replacing the 8PSK modulation with a combined2FSK/8PSK modulation scheme, the improved EDGE system can transmit 4 bits/symbol (compared to 3 bits/symbolof 8PSK) in the same bandwidth as the original EDGE system with similar BER performance. The 2FSK/8PSK modulation can easily be changed to other NFSK/LPSK schemes to trade between performance and speed (e.g. 2FSK/4PSK or 2FSK/16PSK). The combined 2FSK/8PSK modulation scheme requires the receiver to work at 2 samples per symbol to detect the information in the FSK and PSK parts. When the 2FSK/8PSK modulation method is implemented in the EDGE system, the use of suboptimum equalization with prefiltering is required. For the 2FSK/8PSK, we have used a RSSE8 equalizer, where no set partitioning is used, and modified it to handle signal sets of the 2FSK/8PSK modulation. For obtaining a minimum-phase overall impulse response we suggest the use of a MMSE-DFE feedforward filter. By using the EDGE transmit filter, the 2FSK/8PSK signal will suffer from severe ISI and, in practice, some symbol sequences cannot be distinguished from one another. This could be compensated by using a different transmit filter or by a suitable channel coding scheme. The newtransmit filter should be designed so that the ISI caused by the filter would be eased, compared to the present EDGE transmit filter, without breaking the spectral requirements of the standard , when used with the 2FSK/8PSK modulation. On the other hand, similar channel coding schemes,as those used in the current GSM EDGE, should be

designedfor

2FSK/8PSK

EDGE

to

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into

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theproperties of the combined odulation scheme.

CONCLUSION

In this paper we propose a power and spectral efficientNFSK/LPSK modulation scheme to be used in EDGE for improved terrestrial mode and satellite communications. The preliminary simulation results verify the feasibility of the NFSK/LPSK modulation as an efficient modulation method to be used in the EDGE system. We showed that by changing the 8PSK modulation in EDGE to 2FSK/8PSK, in the AWGN channel the data transmission speed can be increased without loss of performance. In the case of FSK/8PSK the one extra bit can be used to increase the data transmission speed or lower the transmitter power, by using the extra bit for improving channel coding.The main focus of our future work is on designing a new Gaussian transmit filter and

suitable coding schemes for NFSK/LPSK EDGE to combat ISI so that spectral and power efficiency of the existing EDGE can be improved.

CHANNEL CODING AND FRAME STRUCTURE

Although EDGE is a highly sophisticated radio technology, it uses the same radio channels and timeslots as any GSM and GPRS system, so it does not require additional spectral resources except to accommodate loading. By deploying EDGE, operators can use their existing spectrum more efficiently. Most new GSM networks deployed today include EDGE. For many GSM/GPRS networks in areas such as the Americas, EDGE was

mostly a software upgrade to the Base Transceiving Station (BTS) and the BSCs, as the transceivers in these networks are already EDGE capable. Some carriers have reported the cost of upgrading to EDGE from GSM/GPRS to be as low as $1 to $2 per POP26. The same packet infrastructure supports both GPRS and EDGE. An increasing number of GPRS terminals support EDGE, thus making EDGE available to more subscribers. Many operators that originally planned to use only UMTS for nextgeneration data services have deployed or are now deploying EDGE as a complementary 3G technology. There are multiple reasons for this, including: 1. EDGE provides a high-capability data service in advance of UMTS. 2. EDGE provides average data capabilities for the sweet spot of approximately 100 kbps, enabling many communications-oriented applications. 3. EDGE has proven itself in the field as a cost-effective solution and is now a mature technology. 4. EDGE is very efficient spectrally, allowing operators to support more voice and data users with existing spectrum.

5.

Operators

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EDGE

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complementary service offering, even as they deploy UMTS/HSPA. 6. EDGE provides a cost-effective wide-area data service that offers continuity and that is complementary with a UMTS/HSDPA network deployed in high traffic areas. It is important to note that EDGE technology is continuing to improve. For example, Release 4 significantly reduced EDGE latency (network round-trip time)from the typical 500 to 600 msec to about 300 msec. Release 7 will also include significant new features for EDGE. Devices themselves are increasing in capability. Dual Transfer Mode (DTM) devices, already available from vendors, will allow simultaneous voice and data communications with both GPRS and EDGE devices. For example, during a voice call users will be able to retrieve e-mail, do multimedia messaging, browse the Web, and do Internet conferencing. This is particularly useful when connecting phones to laptops via cable or Bluetooth and using them as modems.

DTM is a 3GPP-specified technology that enables new applications like video sharing while providing a consistent service experience (service continuity) with UMTS. Typically, a DTM end-to-end solution requires only a software upgrade to the GSM/EDGE radio network.

EDGE EvolutionRecognizing the value of the huge installed base of GSM networks, 3GPP is currently working to improve EDGE capabilities for Release 7. This work is part of the GERAN Evolution effort, which also includes voice enhancements not discussed in this paper. Although EDGE today already serves many applications, such as wireless e-mail, extremely well, it makes good sense to continue to evolve EDGE capabilities. From an economic standpoint, it is less costly than upgrading to UMTS because most enhancements are designed to be software based, and highly asset efficient because it involves less long-tem capital investments to upgrade an existing system. With 82 percent of the world market using GSM, which is already equipped for simple roaming and billing, it is easy to offer global service to subscribers. Evolved EDGE offers higher data rates and system capacity; cable modem speeds are realistically achievable. Evolved EDGE mobiles will be much less expensive and offer greater talk and standby times than UMTS mobiles. UMTS mobile stations also incorporate

GSM capability, and two radios are more expensive and consume more power than one radio. Evolved EDGE also provides better service continuity between EDGE and HSPA, meaning that a user will not have a hugely different experience when moving between environments. Although GSM and EDGE are already highly optimized technologies, advances in radio techniques enable further efficiencies. Some of the objectives of Evolved

EDGE include: A 100-percent increase in peak data rates. A 50-percent increase in spectral efficiency and capacity in C/I-limited scenarios. A sensitivity increase in the downlink of 3 dB for voice and data Reduction of latency for initial access and round-trip time, enabling support for conversational services such as VoIP and PoC Achieving compatibility with existing frequency planning, thus facilitating deployment in existing networks Coexisting with legacy mobile stations by allowing both old and new stations to share the same radio resources Avoiding impacts on infrastructure by enabling improvements through a software upgrade Applicability for DTM (simultaneous voice and data) and the A/Gb mode interface. The A/Gb mode interface is part of the 2G core network, so this goal is required for full backward compatibility with legacy GPRS/EDGE The methods being standardized in

Release 7 to achieve these objectives include: Adding 16 Quadrature Amplitude Modulation (16-QAM) and a new set of modulation/coding schemes that will increase maximum throughput per timeslot by 38 percent. Currently, EDGE uses 8PSK modulation. Simulations indicate a realizable 25 percent increase in user-achievable peak rates. Allowing reception on two distinct radio channels to increase the number of simultaneous timeslots. A type 2-enhanced EDGE device (which can simultaneously transmit and receive) will be able to receive up to 16 timeslots in two radio channels as well as transmit on up to eight timeslots in one radio channel. Mobile Broadband: EDGE, HSPA, LTE Page 21 Reducing the Transmission Time Interval (TTI) to reduce overall latency. This will have a dramatic effect on application throughput for many applications. Downlink diversity reception of the same radio channel to increase the robustness in interference and improve the receiver sensitivity. Sensitivity gains of 3 dB and a decrease in required C/I of up to 18 dB for a single co-channel interferer are shown in simulations. Significant increases in system capacity can be achieved, as explained below. Dual-Carrier Receiver A key part of the evolution of EDGE is the utilization of more than one radio frequency carrier. This overcomes the inherent limitation of the narrow channel bandwidth of GSM. Using two radio-frequency carriers requires two receiver chains in the downlink, as shown in the following figure. Using two carriers enables the reception of twice as many radio blocks simultaneously or, alternatively, the original number of radio blocks can be divided between the two carriers, thus

reducing the transmission time by half, and avoiding the potential need for simultaneous transmission and reception. Channel capacity with dual-carrier reception improves greatly, not by increasing basic efficiencies of the air-interface but because of statistical improvement in the ability to assign radio resources, which increases trunking efficiency. As network loading increases, it is statistically unlikely that contiguous timeslots will be available. With todays EDGE devices, it is not possible to change radio frequencies when going from one timeslot to the next. However, with an Evolved EDGE dual receiver this becomes possible, thus enabling contiguous timeslots across different radio channels. Figure 7 shows a dual-radio receiver approach optimizing the usage of available

Higher Order Modulation Schemes The addition of higher order modulation schemes enhances EDGE network capacity with little capital investment by extending the range of the existing wireless technology. More bits per symbol mean more data transmitted per unit time. This yields a fundamental technological improvement in information capacity and faster data rates. Use of higher order modulation exploits localized optimal coverage circumstances, thereby taking advantage of the geographical locations associated with probabilities of high C/I ratio and enabling very high data transfer rates whenever possible. These enhancements are only now being considered because factors such as processing power and variability of interference and signal level made higher order modulations impractical for mobile wireless systems just a few years ago. However, newer techniques for demodulation, such as advanced receivers and receive diversity, help enable their use. Realization of 16-QAM is planned for Release 7. Advanced equalizer research has shown that 32 and 64-QAM are also possible, and this is currently being studied for future releases. Table 3 shows the theoretical peak throughput for four slots and considers only fundamental improvements, shown in the new Evolved EDGE Modulation and Coding Scheme (MCS) 10 and MCS 11.

EDGE Deployment and MigrationGSM operators first enhanced their networks to support data capability through the addition of GPRS infrastructure, with the ability to use existing cell sites, transceivers, and interconnection facilities. Operators more recently deploying GSM installed GSM and GPRS simultaneously; these included AT&T Wireless (now part of Cingular), Cingular Wireless, Rogers Wireless, and Telecom Personal. Lately, operators have been upgrading their PRSnetworks to EDGE, with extremely good results.Operators are now deploying UMTS worldwide. Although UMTS involves a new radio-accessnetwork, several factors facilitate deployment. Firstly, most UMTS cell sites can be

collocated in GSM cell sites enabled by multi-radio cabinets that can accommodate GSM/EDGE as well as UMTS equipment. secondly, much of the GSM/GPRS core network can be used. While the SGSN needs to be upgraded, the mobile switching center needs only a simple upgrade and the GGSN can stay the same. New features such as HSDPA, HSUPA, and MBMS (discussed earlier) are being designed so the same upgraded UMTS radio channel can support a mixture of terminals, including those based on 3GPP Release 99, Release 5, and Release 6. In other words, a network supporting Release 5 features (e.g., HSDPA) can support Release 99, Release 5, and Release 6 terminals (e.g., HSUPA) operating in a Release 5 mode. Alternatively, a network supporting Release 6 features can support Release 99, Release 5, and Release 6 terminals. This flexibility assures the maximum degree of forward and backward compatibility. Note also that most UMTS terminals today support GSM, facilitating use across large coverage areas and multiple networks.

Advantages

Downlink peak data rates up to 100 Mbps with 20 MHz bandwidth Uplink peak data rates up to 50 Mbps with 20 MHz bandwidth Operation in both TDD and FDD modes Scalable bandwidth up to 20 MHz, covering 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz in the study phase. 1.6 MHz wide channels are under consideration for the unpaired frequency band, where a TDD approach will be used Increase spectral efficiency over Release 6 HSPA by a factor of two to four Reduce latency to 10 msec round-trip time between user equipment and the base station and to less than 100 msec transition time from inactive to active

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