HSDPA EVOLUTION OF HSDPA

Transcription

1 INTRODUCTION 3G HSDPA High Speed Downlink Packet Access is an upgrade to the original 3G UMTS cellular system (3.5G) that provides a much greater download speeds for data. With more data being transferred across the downlink than the uplink for datacentric applications, the upgrade to the downlink was seen as a major priority. Accordingly 3G UMTS HSDPA was introduced into the 3GPP standards as soon as was reasonably possible, the uplink upgrades following on slightly later.3g UMTS HSDPA significantly upgrades the download speeds available, bring mobile broadband to the standards expected by users. With more users than ever using cellular technology for s, Internet connectivity and many other applications, HSDPA provides the performance that is necessary to make this viable for the majority of users. When HSDPA will be implemented, it can coexist on the same carrier as the current Release 99 WCDMA services. This will enable a smooth and cost-efficient introduction of HSDPA into the existing WCDMA networks. The driving force for high data rates are greater speed, shorter delays when downloading audio, video and large files which will be used in PDA s, smart phones etc. Further a user can download packet data over HSDPA, while at the same time having a speech call. HSDPA offers theoretical peak rates of up to 10MBps and in practice more than 2MBps. The technical aspects behind the HSDPA concept include the following: 1. Shared channel transmission 2. Adaptive Modulation and Coding (AMC) 3. Fast Hybrid Automatic Repeat Request (H-ARQ) 4. Fair and fast scheduling at Node B 5. Fast cell site selection (FCSS) 6. Short transmission time interval (TTI) BM II COLLEGE OF ENGINEERING 1 DEPT. OF ECE

2 EVOLUTION OF HSDPA The second generation (2G) of mobile cellular systems has been developed as a successor of analogue systems (called 1G) and became a commercial success in the middle 90's. 2G systems cover a certain number of different technologies among which the most important are: (1) Global System for Mobile Communications (GSM), the more developed technology in the world, in Europe, in many African, Asian and Middle-East countries, and also in American countries (USA, Canada and a lot of South America countries), (2) cdmaone (also called IS-95), mainly used in the America and Asia-Pacific regions, (3) IS-136 (TDMA, also called D-AMPS), used in North and South America and (4) Personal Digital Cellular (PDC), used only in Japan. These systems offer circuit switched voice and rather limited data rate (e.g. 9.6 Kbps for GSM circuit mode), which nevertheless opened a new market for mobile data communications through the Short Message Service (SMS). BM II COLLEGE OF ENGINEERING 2 DEPT. OF ECE

3 The demand for higher data rates has led to the development of so-called "2G+" or "2.5G" systems. For the GSM technology, the first step has been General Packet Radio Service (GPRS) which offers packet switched transmission at bit rates of about 40 kb/s by allocating several time slots of a frame to the same data transmission. The second step for GSM has been Enhanced Data rates for GSM Evolution (EDGE), which mainly consists in the introduction of the 8-PSK modulation, multiplying by 3 the on-line date rate compared to GPRS. Indeed, EDGE is included in the 3G IMT-2000 family of systems. IS-95 and IS-136 have also evolved in the same direction. IS-95-HDR implements a packet mode at 144 kb/s (first step towards CDMA2000), while IS-136 has evolved to an EDGE-GSM-based system under the name of Universal Wireless Communications 136 (UWC-136). These technical evolutions aiming to provide more and more efficient data services have paved the way for the definition of 3G systems. The ITU has deployed a lot of efforts to define a family of systems, called 3G systems, which provide high data rate to offer multimedia services. Under the name International Mobile Telecommunications 2000 (IMT-2000), these systems have been designed for use in the frequency bands selected by the World Radio Conference (WRC) in the year The IMT-2000 family is composed of five systems: (1) Wideband Code Division Multiple Access (W-CDMA) including TDD and FDD modes, (2) CDMA X, (3) Time Division Synchronous Code Division Multiple Access (TD-SCDMA), (4) EDGE (also called UWC-136) and (5) Digital Enhanced Cordless Telecommunications (DECT). At the end of the selection phase for IMT-2000, two main families of systems have emerged, leading to the creation of two groups of standardization (including operators and manufacturers), namely: (1) 3 rd Generation Partnership Project (3GPP), which developed the W-CDMA standard also called Universal Mobile Telecommunication System (UMTS) in FDD and TDD modes, and (2) 3GPP2, which developed the CDMA 2000 standards as an evolution of the IS-95 standards. BM II COLLEGE OF ENGINEERING 3 DEPT. OF ECE

4 The new high speed technology is part of the 3G UMTS evolution. It provides additional facilities that are added on to t e basic 3GPP UMTS standard. The upgrades and additional facilities were introduced at successive releases of the 3GPP standard. Release 4: This release of the 3GPP standard provided for the efficient use of IP, a facility that was required because the original Release 99 focused on circuit switched technology. Accordingly this was a key enabler for 3G HSDPA. Release 5: This release included the core of HSDPA itself. It provided for downlink packet support, reduced delays, a raw data rate (i.e. including payload, protocols, error correction, etc) of 14 Mbps and gave an overall increase of around three over the 3GPP UMTS Release 99 standard. Release 6: This included the core of HSUPA with an enhanced uplink with improved packet data support. This provided reduced delays, an uplink raw data rate of 5.74 Mbps and it gave an increase capacity of around twice that offered by the original Release 99 UMTS standard. Also included within this release was the MBMS, Multimedia Broadcast Multicast Services providing improved broadcast services, i.e. Mobile TV. Release 7: This release of the 3GPP standard included downlink MIMO operation as well as support for higher order modulation up to 64 QAM in the uplink and 16 QAM in the downlink. However it only allows for either MIMO or the higher order modulation. It also introduced protocol enhancements to allow the support for Continuous Packet Connectivity (CPC). Release 8: This release of the standard defines dual carrier operation as well as allowing simultaneous operation of the high order modulation schemes and MIMO. Further to this, latency is improved to keep it in line with the requirements for many new applications being used. BM II COLLEGE OF ENGINEERING 4 DEPT. OF ECE

5 HSDPA PRINCIPLE HSDPA is based on a combination of technologies. Significant is the introduction of a new transmission channel for the user data, the High Speed (Physical) Downlink Shared Channel, HS-(P) DSCH. Multiple users share the air interface resources available on this channel. An intelligent algorithm in the Node B decides which subscriber will receive a data packet at which time. This decision is reported to the subscribers via a parallel signaling channel, the High Speed Shared Control Channel, HSSCCH. In contrast to UMTS, where a new data packet can be transmitted at least every 10 ms, with HSDPA data packet transmission can occur every 2 ms. Another important innovation is the use of an adaptive modulation and coding procedure. Every subscriber regularly sends messages regarding the channel quality to the Node B. Depending on the quality of the mobile radio channel, the Node B selects a suitable modulation and coding for the data packet that offers satisfactory protection BM II COLLEGE OF ENGINEERING 5 DEPT. OF ECE

6 against transmission errors and that optimizes the use of resources on the air interface. The Node B can select from the modulation methods QPSK (quadrature phase shift keying) and 16QAM (quadrature amplitude modulation). While QPSK is already being used in UMTS release 99, 16QAM provides high data rates specifically for HSDPA. In order to achieve robust data transmission, HSDPA uses a HARQ (Hybrid Automatic Repeat Request) protocol. If a UE receives a data packet with errors, it requests the data packet again. When repeating the packet transmission, the Node B can select a different coding version that provides the subscriber with better reception of the packet (incremental redundancy). This coding version is often referred to as redundancy and constellation version or in short redundancy version (RV version). When a packet has been transmitted to the UE, the Node B has to wait until an acknowledgement (ACK) or negative acknowledgement (NACK) is received for this particular packet (so-called stop-and-wait transmission mechanism).. One UE has to support up to 8 parallel HARQ processes which are equivalent to up to 8 independent HARQ stop-and-wait transmission mechanisms. User feedback about channel quality as well as packet acknowledgements or negative acknowledgements is provided in the uplink on the High Speed Dedicated Physical Control Channel, HS- DPCCH. KEY HSDPA TECHNOLOGY ENHANCEMENTS HSDPA was designed to increase downlink packet data throughput of UMTS by means of: 1. Shared channel transmission 2. Adaptive Modulation and Coding (AMC) 3. Fast Hybrid Automatic Repeat Request (H-ARQ) 4. Fair and fast scheduling at Node B 5. Fast cell site selection (FCSS) 6. Short transmission time interval (TTI) BM II COLLEGE OF ENGINEERING 6 DEPT. OF ECE

7 1. SHARED CHANNEL TRANSMISSION Several new channels are introduced in release 5. A new transport channel named High-Speed Downlink Shared Channel (HS-DSCH) is the primary radio bearer. For the associated signaling a channel called high-speed shared control channel (HS-SCCH) has been added in the downlink and in the uplink the high-speed dedicated HS-(P) DSCH Structure The transport channel HS-DSCH is mapped on one or more physical channels of type HS-PDSCH. The HS-PDSCH is always spread with spreading factor 16. One HS-DSCH transport block is transmitted in a transmission time interval (TTI) of 2 ms (corresponding to 3 timeslots). If UE category allows, HS-DSCH transport blocks can be scheduled to the UE continuously, i.e. in every TTI. Less complex UEs corresponding to a lower UE category can only process data received in every second or even every third TTI. This is described by the so-called inter TTI distance parameter. An inter TTI distance of 1 equals continuous HS-PDSCH transmission (in case data is available for transmission). QPSK or 16QAM are available as modulation scheme on the HS-PDSCH. Figure outlines the structure of the HS-(P) DSCH. STRUCTURE OF HS-(P) DSCH BM II COLLEGE OF ENGINEERING 7 DEPT. OF ECE

8 HS-SCCH Structure The HS-SCCH is a fixed rate downlink physical channel, spread with spreading factor 128. One UE has to monitor up to 4 HS-SCCH channels. The UE is informed by higher layers at call setup which HS-SCCH channels to monitor. The HS-SCCH contains scheduling and control information (UE identification, HS- PDSCH channelization codes, HSPDSCH modulation scheme information, transport block size information, HARQ process information, redundancy and constellation version, new data indicator). Figure outlines the HS-SCCH structure: STRUCTURE OF HS-SCCH The HS-PDSCH starts 2 timeslots after the start of the corresponding HSSCCH. HS-DPCCH Structure The HS-DPCCH is an uplink physical channel used to carry control information: HARQ ACK/NACK and Channel Quality Information. Figure outlines the structure of the HS-DPCCH. STRUCTURE OF HS-DPCCH BM II COLLEGE OF ENGINEERING 8 DEPT. OF ECE

9 The Channel Quality Information consists of a CQI value. There are different CQI tables specified for different UE categories, reflecting the level of UE implementation complexity. The CQI values regularly reported by the UE are interpreted by the Node B as proposal how to format the HS-(P) DSCH. With this format, the resulting block error rate of the HS-DSCH is predicted by the UE to be below 0.1. The higher the CQI value, the more demanding the HS-DSCH transmission format, i.e. the better the radio link quality has to be. 2. ADAPTIVE MODULATION AND CODING (AMC) HSDPA uses both the modulation used in WCDMA, namely Quadrature Phase Shift Keying (QPSK) and under good radio conditions, an advanced modulation scheme, 16 Quadrature Amplitude Modulation (16 QAM). The benefit of 16 QAM is that four bits of data are transmitted in each radio symbol as opposed to two with QPSK. 16 QAM increases data throughput, while QPSK is available under adverse conditions. Depending on the condition of the radio channel, different levels of forward error correction (channel coding) can also be employed. For example, a three quarter coding rate means that three quarters of the bits transmitted are user bits and one quarter is error correcting bits. The process of selecting and quickly updating the optimum modulation and coding rate is referred to as fast link adaptation. QUADRATURE PHASE SHIFT KEYING (QPSK) Sometimes known as quaternary or quadriphase PSK, 4-PSK, QPSK uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER twice the rate of BPSK. Analysis shows that this may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth needed. Although QPSK can be viewed as a quaternary modulation, it is easier to see BM II COLLEGE OF ENGINEERING 9 DEPT. OF ECE

10 it as two independently modulated quadrature carriers. With this interpretation, the even (or odd) bits are used to modulate the in-phase component of the carrier, while the odd (or even) bits are used to modulate the quadrature-phase component of the carrier. BPSK is used on both carriers and they can be independently demodulated. The modulated signal is shown below for a short segment of a random binary datastream. TIMING DIAGRAM OF QPSK SYMBOL CARRIER PHASE TRANSMITTED CONSTELLATION DIAGRAM OF QPSK 16- QUADRATURE AMPLITUDE MODULATION (16- QAM) Data is spit into two channels, I and Q. As with QPSK, each channel can take on two phases. However, 16-QAM also accommodates two intermediate amplitude BM II COLLEGE OF ENGINEERING 10 DEPT. OF ECE

11 values. Two bits are routed to each channel simultaneously. The two bits to each channel are added, and then applied to the respective channel s modulator. CONSTELLATION DIAGRAM OF 16-QAM Table below shows the different throughput rates achieved based on the modulation, the coding rate, SYMBOL CARRIER CARRIER TRANSMITTED PHASE AMPLITUDE and the number of HS-DSCH codes in use. Both Convolutional Coding and Turbo coding are supported but previously only CC has been supported. Note that the peak rate of 14.4 Mbps occurs with a coding rate of 4/4, 16 QAM and all 15 codes in use. MODULATION QPSK CODING RATE THROUGH PUT WITH 5 THROUGH PUT WITH 10 THROUGH PUT WITH 15 CODES CODES CODES 1/4 600kbps 1.2Mbps 1.8 Mbps 2/4 1.2Mbps 2.4 Mbps 3.6 Mbps 3/4 1.8Mbps 3.6 Mbps 5.4 Mbps BM II COLLEGE OF ENGINEERING 11 DEPT. OF ECE

12 16 QAM 2/4 2.4Mbps 4.8 Mbps 7.2 Mbps 3/4 3.6Mbps 7.2 Mbps 10.7 Mbps 4/4 4.8Mbps 9.6 Mbps 14.4 Mbps 3. FAIR AND FAST SCHEDULING AT NODE B It allows the HS-DSCH channel to take advantage of favorable channel conditions to make best use of available radio conditions. Each UE periodically reports on the signal quality to Node B (Base Stations). That information is then used to decide which users will be sent data on the next 2ms frame and how much data can be sent to each user. A first approach for fair scheduling can be Round-Robin method where every user is served in a sequential manner so all the users get the same average allocation time. However, the requirement of high scheduling rate along with the large AMC availability with the HSDPA concept, where the channel is allocated according to the instantaneous channel conditions. Another popular packet scheduling is proportional fair packet scheduling. Here, the order of service is determined by the highest instantaneous relative channel quality. Since the selection is based on relative conditions, still every user gets approximately the same amount of allocation time depending on its channel condition. 4. FAST HYBRID AUTOMATIC REPEAT REQUEST (H-ARQ) Some data will inevitably be corrupted in transit to the device and will have to be retransmitted. With HSDPA, data retransmission may be handled locally by the base-station improving response times compared to earlier UMTS networks (where only the more distant RNC could manage data retransmissions). HSDPA employs a stop and wait hybrid automatic repeat request (SAW HARQ) retransmission BM II COLLEGE OF ENGINEERING 12 DEPT. OF ECE

13 protocol between the base-station and the user device. With HARQ, each device checks the integrity of its received data in each relevant HS-DSCH TTI. If the data is correct, the device returns an ACK (acknowledging receipt of correct data) signal, in which case the base-station can move on to the next set of data. If the data is not successfully received, the device transmits an NACK (negative acknowledgement) and the base-station retransmits the corresponding data. With soft combining at the user device, the earlier set(s) of corrupted data can be combined with subsequently retransmitted data to increase the likelihood of correctly decoding valid data. The AMC uses an appropriate modulation and coding scheme according to the channel conditions. Even after AMC, we may land up with errors in the received packets due to the fact that the channel may vary during the packet is on the fly. An automatic repeat request (ARQ) scheme can be used to recover from these link adaptation errors. When the transmitted packet is received erroneous then the receiver requests the transmitter for the retransmission of that erroneous packet. The basic technique is to use the energy of the previously transmitted signal along with the new retransmitted signal to decode the block. There are two main schemes for H-ARQ, Chase combining and Incremental redundancy. Chase Combining involves the retransmission of the same data packet which was received with errors. Once the retransmission is received, the receiver combines the soft values of the original signal and the retransmitted signal weighted by the SNR prior to decode the data packet. It is advantageous as each transmission and retransmission can be decoded individually (self-decodable), time diversity gain, may be path diversity gain. The main disadvantage is transmission of the entire packet again, which is wastage of bandwidth. BM II COLLEGE OF ENGINEERING 13 DEPT. OF ECE

14 CHASE COMBINING SCHEME Incremental Redundancy is used to get maximum performance out of the available bandwidth. Here the retransmitted block consists of only the correction data to the original data that carries no actual information (Redundancy). The additional redundant information is sent incrementally when the first, second retransmissions are received with errors. It is advantageous as it reduces the effective data throughput/ bandwidth of a user and using this for another user. The main disadvantages are the systematic bits are only sent in the first transmission and not with the retransmission which makes the retransmissions non-self decodable. So, if the first transmission is lost due to large fading effects there is no chance of recovering from this situation. BM II COLLEGE OF ENGINEERING 14 DEPT. OF ECE

15 INCREMENTAL REDUNDANCY Although the HSDPA standard supports both chase combining and incremental redundancy, it has been shown that incremental redundancy performs almost always better than chase combining, at the cost of increased complexity, though. 5. FAST CELL SITE SELECTION (FCSS) HSDPA does not use soft handover. This is because the AMC, H-ARQ and fast packet scheduling are techniques that require a constant one-to-one connection between the HSDPA mobile terminal and the BS. Thus hard handover, in which the destination BS is selected each time the cell changes, is needed. Since the only traffic supported by HSDPA is delay-tolerant data traffic soft handover is also not as necessary as when dealing with voice traffic. 6. SHORTER TRANSMISSION TIME The shorter time interval enables higher speed transmission in the physical layer, so that the system will be more reactive to changing link conditions and can reallocate capacity to users quicker. BM II COLLEGE OF ENGINEERING 15 DEPT. OF ECE

16 HSDPA ARCHITECTURE The protocol structure for HSDPA is outlined in figure. Compared to UMTS release 99, significant functionality has been moved to the Node B in release 5. Thus, new MAC-hs (Medium Access Control high speed) protocol entity has been introduced in the Node B. It is responsible for flow control, scheduling and priority handling of data, control of HARQ processes and selection of appropriate transport formats and resources. The MAC-hs entity is terminated on the UE side. HSDPA PROTOCOL ARCHITECTURE Within the Radio Resource Control (RRC) protocol, existing messages for bearer setup, reconfiguration and release were modified to support HSDSCH. New information elements were introduced, e.g. to inform the UE about the HS-SCCH set to monitor and about the measurement cycle for the CQI reporting. Mobility for HSDPA is based on existing release 99 handover procedures. For the HS-PDSCH no macro diversity is applied, i.e. a specific HSPDSCH is transmitted in a single cell only. BM II COLLEGE OF ENGINEERING 16 DEPT. OF ECE

17 PERFORMANCE OF HSDPA The performance of each technology is determined by a number of constraints, including the throughput, the latency etc. The throughput is the data rate of the standard. The theoretical maximum throughput is the throughput rate available to a single connection under ideal circumstances. These speeds may not be achieved regularly in typical usage. The typical throughput is what users have experienced most of the time when well-within the usable range to the base station. This value is not known for the newest experimental standards. Note that these figures cannot be used to predict the performance of any given standard in any given environment, but rather as benchmarks against which actual experience might be compared. The latency is the time taken for the smallest packet to travel between the user terminal and base station. Just as important as throughput is network latency, defined as the round-trip time it takes data to traverse the network. Each successive data technology from GPRS forward reduces latency, with HSDPA networks having latency as low as 70 milliseconds. HSUPA brings latency down even further, as will 3GPP LTE. Ongoing improvements in each technology mean all these values will go down as vendors and operators fine tune their systems. Figure shows the latency of different 3GPP technologies. LATENCY OF DIFFERENT TECHNOLOGIES BM II COLLEGE OF ENGINEERING 17 DEPT. OF ECE

18 Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol, and sometimes by the media access control (the channel access protocol). NET BIT RATE PER FREQUENCY BANDWIDTH PER FREQUENCY SPECTRAL EFFICIENCY CHANNEL (Mbps) CHANNEL (MHz) (bps/hz/site) GSM EDGE WCDMA HSDPA LTE COMPARISON WITH WCDMA (R 99) 3GPP s Release 99 specified the first UMTS 3G network. The technology used in R 99 systems is called W-CDMA. HSDPA is a high speed data enhancement to WCDMA systems like EDGE was for GSM/GPRS and will most often be deployed with an R 99 system. That is WCDMA is used for voice and HSDPA for data on the same network, they will thus have to share bandwidth and power. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems. WCDMA (R 99) HSDPA Modulation Scheme QPSK QPSK, 16- QAM Downlink Multiple CDMA CDMA- TDMA Access Uplink Multiple Access CDMA CDMA Duplex Method FDD FDD Channel Bandwidth 5 MHz 5MHz Frame Size 10 ms 2 ms Coding CC CC, Turbo Downlink Peak Data 384 Kbps 14.4 Mbps Rate COMPARISON WITH COMPETING TECHNOLOGIES BM II COLLEGE OF ENGINEERING 18 DEPT. OF ECE

19 Competing wireless technologies with HSDPA are Mobile WiMAX (IEE e) and 1X EvDo in CDMA COMPARISON WITH MOBILE WIMAX AND EV- DO HSDPA and Mobile WiMAX are high speed mobile technologies with different backgrounds. HSDPA is a data enhancement for a voice-centric 3GPP system while WiMAX is data-centric broadband technology that has an added feature of mobility. Many operators around the world have invested in R 99 UMTS networks. For them HSDPA offers a significant service upgrade and an opportunity to accelerate the Return of Investment. HSDPA networks are already widely deployed and handsets have been on the market since For Mobile WiMAX it is necessary to build new networks, and the manufacturing of handsets has been quite complicated and required a totally new set of chips and platforms. EvDo is standardized by 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world particularly those previously employing CDMA networks. It is also used on the Globalstar satellite phone network Despite their different background there are several technical features that the three technologies have in common. Those include Adaptive Modulation and Coding (AMC), Hybrid ARQ and Fast Scheduling. In OFDMA systems users are allocated different portions of the channel where as in CDMA each user transmits over the entire channel. This means that in OFDMA there is no multiple access interference (MAI) between multiple users. In CDMA orthogonal spreading codes are used to avoid MAI but due to the uplink synchronization issues, asynchronous CDMA is used in the uplink in most practical CDMA systems and there will be interference and reduced spectral efficiency. As only a portion of the channel is occupied by the WiMAX signals frequency selective BM II COLLEGE OF ENGINEERING 19 DEPT. OF ECE

20 scheduling can be used to choose sub channels with the best condition at each time and hence improve QoS. For smart antenna technologies the processing complexity scales with the channel bandwidth. Since in CDMA the signals occupy the entire bandwidth this becomes quite a problem when used in broadband wireless channels and limits the options of using advanced Antenna Technology. OFDMA on the other hand is well suited for these technologies. Mobile WiMAX will most commonly use TDD while HSDPA generally uses FDD. FDD is more efficient than TDD in the case of symmetric traffic but TDD allow for asymmetric traffic and as the downlink traffic is usually much heavier than the uplink traffic, asymmetric traffic can be very practical. TDD requires system-wide frame synchronization to counter interference issues and the discontinuous transmissions reduce the average power. On the other hand TDD assures channel reciprocity and thus better supports link adaptation, MIMO and other advanced antenna technologies. The 60% longer radius of HSDPA gave it an advantage in economic feasibility while 70% higher throughput for Mobile WiMAX did not give any economic advantage. The performance of HSPA and Mobile WiMAX technologies is comparable: Mobile WiMAX does not offer any technology advantage over HSPA. Both technologies offer similar peak data rates, spectral efficiency and network complexity. However, Mobile WiMAX requires more sites to offer the same coverage and capacity as HPSA. EvDo is standardized by 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world particularly those previously employing CDMA networks. It is also used on the Globalstar satellite phone network. EV-DO uses many of the same techniques for optimizing spectral efficiency as HSPA, including higher order modulation, efficient scheduling, turbo-coding, and adaptive modulation and coding. For these reasons, it achieves spectral efficiency that is virtually the same as HSPA. The 1x technologies operate in the 1.25 MHz radio channels, compared to the 5 MHz channels UMTS uses. This result in lower theoretical peak rates, but average throughputs for high level of network loading is similar. Under low to medium-load BM II COLLEGE OF ENGINEERING 20 DEPT. OF ECE

21 conditions, because of the lower peak achievable data rates, EV-DO or EVDO Rev A achieves a lower typical performance level than HSPA. Operators have quoted 400 to 700 kilobits per second (kbps) typical downlink throughput for EV-DO Rev 035 and between 600 kbps and 1.4 Mbps for EV-DO Rev A.36. One challenge for EV-DO operators is that they cannot dynamically allocate their entire spectral resources between voice and high-speed data functions. The EV- DO channel is not available for circuit-switched voice, and the 1xRTT channels offer only medium speed data. In the current stage of the market, where data only constitutes a small percentage of total network traffic, this is not a key issue. But as data usage expands, this limitation will cause suboptimal use of radio resources. Another limitation of using a separate channel for EV-DO data services is that it currently prevents users from engaging in simultaneous voice and high-speed data services, whereas this is possible with UMTS and HSPA. Many users enjoy having a tethered data connection from their laptop by using Bluetooth, for example and being able to initiate and receive phone calls while maintaining their data sessions. HSDPA Mobile WiMAX EV-DO Base Standard WCDMA IEEE e CDMA 2000 Duplex Method FDD TDD FDD Downlink Multiple CDMA-TDMA OFDMA TDM Access Uplink Multiple Access CDMA OFDMA CDMA Frequency 900MHz/1.8/2.1GHz 2.3/2.5/3.5GHz 450/850/900Mhz/1.8G Hz Channel Bandwidth 5MHz Scalable: 5, 7,8.75, 1.25MHz 10MHz Frame Size DL= 2ms, UL =10ms 5ms DL=1.67ms, UL=6.67ms Modulation Downlink QPSK, 16-QAM QPSK, 16-QAM,64- QPSK, 8-PSK, 16-QAM QAM Modulation Uplink BPSK, QPSK QPSK, 16-QAM BPSK,QPSK, 8-PSK Coding CC, Turbo CC, Turbo CC, Turbo Downlink Peak Data 14.4Mbps 46Mbps 2.45Mbps Rate Uplink Peak Data Rate 2.3Mbps 46Mbps 0.15Mbps Scheduling Fast scheduling in DL Fast scheduling in DL, UL Fast scheduling in DL BM II COLLEGE OF ENGINEERING 21 DEPT. OF ECE

22 H-ARQ Chase Combining Chase Combining Incremental Redundancy Handoff Network Initiated Hard Handoff Network Optimized Hard Handoff Virtual Soft Handoff Coverage 3 Miles <2 Miles >3 Miles Mobility High Low/ Mid High CURRENT DEPLOYMENT OF HSDPA HSDPA (High Speed Downlink Packet Access) is an upgrade to UMTS/WCDMA. HSDPA increases the download speeds by up to 3.5 times, initially delivering typical user data rates of 550 to 800 kbps. Improvements to the downlink, through HSDPA, were the first upgrade steps available to operators seeking to deploy mobile broadband services as a part of 3GPP Release 5. HSDPA speeds are ideal for bandwidth-intensive applications, such as large file transfers, streaming multimedia and fast Web browsing. HSDPA also offers latency as low as 70 to 100 milliseconds (ms) making it ideal for real-time applications such as interactive gaming and delaysensitive business applications such as Virtual Private Networks. High Speed Downlink Packet Access is predominately a software upgrade to Release 99 of the UMTS standard. HSDPA has been commercially available since December 2005, when Cingular Wireless now AT&T launched the world's first large scale HSDPA service. There are more than 300 HSDPA networks commercially deployed or in various stages of deployment in more than 115 countries (May 2009). International roaming is available as the technology falls back on UMTS, EDGE and GPRS for the continuation of voice and data services. Sony Ericsson Z-50, K850i, W910iare some HSDPA supported handsets available in markets. In November 2003, Motorola became the first vendor to demonstrate HSDPA on a commercially available UMTS base station at its Swindon, UK facility. HSDPA supported Motorola handsets are RAZRZ8 and RAZRV9. Nokia N95, E51, E90, 6120Clasic are some HSDPA supported handsets from Nokia which can provide a maximum downlink speed of 3.6Mbps.HSDPA devices also include 39 wireless routers, 61 laptops and 100 devices for laptop connectivity (USB modems etc). The number of HSDPA networks, devices and subscribers is constantly growing. For example BM II COLLEGE OF ENGINEERING 22 DEPT. OF ECE

23 WCDMA/HSDPA was responsible for 75% of the mobile subscription growth in Western Europe in In India MTNL DOLPHIN has started 3G Services under the brand name of 3G Jadoo where Jadoo means Magic in Hindi. While BSNL has launched 3G HSDPA services with speed up to 2 Mbit/s at 12 Indian Cities on The BSNL s Commercial 3G service are available now in Amabala, Agara, Dehardun, Jammu, Jaipur, Jalandhar, Lacknow, Shimla, Patna, Ranchi, Haldia and Durgapur. They are collaborating with Nokia, Sony and Samsung for offering 3G capable mobile handsets along with packages in the market. HSDPA usually requires only new software and base station channel cards, instead of necessitating the replacement of major pieces of infrastructure from UMTS and does not require additional spectrum for deployment. As a result, UMTS operators can deploy HSDPA quickly and cost-effectively. In fact, most operators that deploy 3G UMTS are deploying an HSDPA-ready network. HSDPA technology significantly improves the UMTS downlink performance through techniques, such as adaptive modulation and coding, hybrid ARQ (HARQ) and fast scheduling. On the receiving side, initial HSDPA User Equipment (UE) solutions were based on single antenna CDMA rake receiver structures, similar to Release 99 UMTS receiver structures. The corresponding minimum performance requirement for HSDPA rake receivers was specified in Release 5. While the single antenna rake receivers worked very well for conventional UMTS and met initial system needs for HSDPA, advanced receiving technologies were later used to achieve even higher HSDPA throughputs. To achieve this goal, 3GPP studied two applicable techniques (receive diversity and advanced receiver architectures) as well as their minimum performance improvement and has specified them in Release 6. HSDPA also benefits operators by making more efficient use of spectrum, up to three times more capacity than UMTS. This efficiency means that operators can easily and cost-effectively accommodate more users and services without having to buy additional spectrum just to keep up with growth. That efficiency also reduces operators' overhead costs, and thus, makes them better able to price their services at a point that is competitive yet profitable. BM II COLLEGE OF ENGINEERING 23 DEPT. OF ECE

24 HSDPA is backward-compatible with UMTS, EDGE and GPRS. This design benefits customers when they travel to areas that have not yet been upgraded to HSDPA, as their HSDPA-enabled handsets and modems will still provide fast packetdata connections. This design also benefits operators and application developers because applications designed for UMTS also run on HSDPA networks and devices. HSDPA benefits from the scope and scale of the GSM ecosystem of vendors. Vendors currently offer more than 1,300 models of HSPA/HSDPA devices at a variety of price points. Besides handsets and PC card modems, HSPA/HSDPA is also embedded in many laptops from major vendors such as Acer, Dell, Fujitsu Siemens, HP, Lenovo and Panasonic. Embedded modems are particularly attractive to enterprises because CIOs and IT managers do not have to worry about whether a particular modem is compatible with a particular laptop model. Devices also are available at most GSM frequencies, enabling global roaming. DEPLOYMENT CHALLENGES: INDIAN FACTS Since there is no copper laid out in rural India, DSL is not an option to deliver high bandwidth services. Given the existing and potential coverage realized by GSM/ GPRS cellular systems, the incremental cost of implementing HSDPA should be much lower than that of setting up any other Greenfield wireless network. WiMAX could be a challenger, but its maturity is currently much lower than HSDPA. India has seen a rapid increase in wireless coverage. GSM and CDMA are the competing technologies. As of July 2009, the wireless penetration at million is significantly higher than landline penetration, which is at million. The monthly cellular additions are getting closer to 3 million/month, with GSM technology base having a higher subscriber base accounting for about 80%. GSM coverage enables quick and easy HSDPA access. As can be seen, the range of HSDPA is severely limited to around 2Km cells, as compared the current GSM/GPRS systems that have range that is one order of magnitude higher. This could mean that the current BM II COLLEGE OF ENGINEERING 24 DEPT. OF ECE

25 GSM/GPRS infrastructure is largely insufficient for HSDPA coverage, and significant additional capex may be required to deploy HSDPA into rural areas. The entire cost benefit gains of HSDPA due to its higher capacity could thus be offset due to the cost increase due to lower range. Increasing the range of HSDPA is a key research problem that determines its success for rural India. Lower frequencies reach further. Lower rate transmissions can span a higher range. RELEASES BEYOND HSDPA Work is now staring on developing the standards for High Speed Uplink Packet Access (HSUPA) to improve the data rates on the 3G W-CDMA mobile or cell phone standard. With the cellular telecommunications standards established and work progressing to introduce the equipment for High Speed Downlink Packet Access (HSDPA), the standards are now starting to be developed to enable the uplink from the mobile handset or User Equipment (UE) to the base station (Node B) to be able to handle data at similar speeds. This is known as HSUPA and it will enable new features including full video conferencing to be introduced. 3G HSPA of High Speed packet Access is the combination of two technologies. 3G HSPA is widely deployed and providing significantly increased data transfer rates required for the variety of data applications including mobile broadband for Internet connectivity now being used by mobile users. As 3G UMTS HSPA is normally a relatively straightforward upgrade based around a software change, its incorporation involves a relatively low cost upgrade. As the use of 3G HSPA is able to increase the efficiency of the overall network, reducing the cost per bit, then it is often a very cost effective upgrade. Evolved HSPA provides HSPA data rates up to 42 Mbit/s on the downlink and 22 Mbit/s on the uplink with MIMO technologies and higher order modulation. MIMO on CDMA based systems acts like virtual sectors to give extra capacity closer to the mast. The 42Mbit/s and 22Mbit/s represent theoretical peak sector speeds. The actual peak speed for a user closer to the mast may be about 14Mbit/s. As of August BM II COLLEGE OF ENGINEERING 25 DEPT. OF ECE

26 2009, there are 10 HSPA+ networks running in the world at 21Mbit/s and the first 28Mbit/s network has been completed in Italy. The first to launch was Telstra in Australia in late 2008, with Australia-wide access in February 2009 with speeds up to 21Mbit/sec. LTE (Long Term Evolution) is the last step toward the 4th generation of radio technologies designed to increase the capacity and speed of mobile telephone networks. Where the current generation of mobile telecommunication networks are collectively known as 3G (for "third generation"), LTE is marketed as and called 4G insinuating that it's the "fourth generation". The LTE specification provides downlink peak rates of at least 100 Mbps, an uplink of at least 50 Mbit/s and RAN round-trip times of less than 10ms. LTE supports scalable carrier bandwidths, from 20 MHz down to 1.4 MHz and supports both Frequency Division Duplexing and Time Division Duplexing. CONCLUSION The HSDPA concept facilitates peak data rates exceeding 2 Mbps and theoretically reaching 10 Mbps. The cell throughput gain over previous releases has been evaluated to be in the order of % or more, which is highly dependent on factors such as the radio environment and the service provision strategy of the network operator. Practical HSDPA user bit rates even in large macro cells can be similar to broadband home DSL lines. As HSDPA enables more bits to be transferred with the same radio frequency, it also enables lower cost per bit than Release'99 based WCDMA. The H-ARQ technique which is best suited in HSDPA would be partial incremental redundancy. Performance of partial IR is in between chase combining and IR. Further evolution of HSDPA peak data rates can be achieved with multiple-input multiple-output (MIMO) antenna techniques of 3GPP Rel.'6. No changes are required to the networks except increased capacity within the infrastructure to support the higher bandwidth. REFERENCES BM II COLLEGE OF ENGINEERING 26 DEPT. OF ECE

27 1. 3rd Generation Partnership Project (3GPP). Available at: rd Generation Partnership Project 2 (3GPP2). Available at: 3. Global Mobile Suppliers Association (GSA). Available at: 4. WiMAX Forum, 5. P. Rysavy, 3G Americas. Mobile Broadband: EDGE, HSPA and LTE. Available at: 6. Comparison of Mobile WiMAX and HSDPA: Kolbrun Johanna Runarsdottir 7. Wikipedia contributors, "UMTS frequency bands," title=umts_frequency_bands&oldid= High-Speed Downlink Packet Access - Wikipedia, the free encyclopedia GLOSSARY OF TERMS 1xEV-DO One Carrier Evolved, Data Optimized 1xEV-DV One Carrier Evolved, Data Voice 2G Second Generation 3G Third Generation 3GPP 3G Partnership Project 3GPP2 3G Partnership Project 2 4G Fourth Generation ACK Acknowledgement ADSL Asynchronous Digital Subscriber Line AMC Adaptive Modulation and Coding ARQ Automatic Repeat Request BTS Base Station CDMA Code Division Multiple Access DPCH Dedicated Physical Channel BM II COLLEGE OF ENGINEERING 27 DEPT. OF ECE

28 DL EDGE E-UTRAN FDD FP GPRS GSM GSMA HLR HO HSDPA HSPA HSUPA H-ARQ ITU IEEE LAN LTE MAC MAC-hs MIMO MMS MS MSC NACK OFDMA PER PHY PSTN QAM QoS QPSK RAN Downlink Enhanced Data Rates for GSM Evolution Enhanced UMTS Terrestrial Radio Access Network Frequency Division Multiplex Frame Protocol General Packet Radio Service Global System for Mobile communication GSM Association Home Location Register Handover, Handoff High Speed Downlink Packet Access High Speed Packet Access High Speed Uplink Packet Access Hybrid- ARQ International Telecommunication Union Institute of Electrical and Electronic Engineers Local Area Network Long Term Evolution Media Access Control Medium Access Control high speed Multiple Input Multiple Output Multimedia Message Service Mobile Station Mobile Switching Centre Negative Acknowledgement Orthogonal Frequency Division Multiple Access Packet Error Rate Physical layer Public Switched Telephone Network Quadrature Amplitude Modulation Quality of Service Quadrature Phase Key Shifting Radio Access Network BM II COLLEGE OF ENGINEERING 28 DEPT. OF ECE

29 RF RL RNC SGSN SIM SIMO SMS SNR TDD TDMA TTI UE UL UMTS UTRAN VoIP VPN WCDMA WiFi WAP WiBro WiMAX Radio Frequency Reverse Link (also Radio Link) Radio Network Controller Serving GPRS Support Node Subscriber Identification Module Single Input Multiple Output Short Message Service Signal-to-Noise Ratio Time Division Duplex Time Division Multiple Access Transmission Time Interval User Equipment Uplink Universal Mobile Telephony System UMTS Terrestrial Radio Access Network Voice over IP Virtual Private Network Wideband CDMA Wireless Fidelity Wireless Application Protocol Wireless Broadband Worldwide Interoperability for Microwave Access BM II COLLEGE OF ENGINEERING 29 DEPT. OF ECE