MAY 2014 MOBILE Study Paper on High Speed Packet Access+ (HSPA+) ©TEC TELECOMMUNICATION ENGINEERING CENTRE KHURSHID LAL BHAWAN, JANPATH NEW DELHI - 110001 INDIA 1 Introduction ..............................................................................................................................................................................1 2 Background ...............................................................................................................................................................................1 2.1 HSDPA (Release-5) ................................................................................................................... 1 2.2 HSUPA (Release-6):.................................................................................................................. 2 2.3 HSPA+ (3GPP Release-7 and onwards) .................................................................................... 3 3 High Speed Packet Access Evolution, HSPA+ ....................................................................................................3 3.1 Higher order Modulation ......................................................................................................... 3 3.2 MIMO ...................................................................................................................................... 3 3.3 Advanced receivers ................................................................................................................. 4 3.4 Continuous Packet Connectivity (CPC) ..................................................................................... 4 3.5 Fast Dormancy ......................................................................................................................... 5 3.6 Enhanced FACH and Enhanced RACH....................................................................................... 6 3.7 Layer-2 Enhancements ............................................................................................................ 7 3.8 HSPA+ Architecture Evolution ................................................................................................. 8 3.9 Dual carrier HSPA+ .................................................................................................................. 9 3.10 CS Voice over HSPA ............................................................................................................... 11 3.11 Downlink Multiflow Transmission: ........................................................................................ 12 3.12 Present eco system and evolution step ................................................................................. 13 4 Conclusion............................................................................................................................................................................... 13 5 References ............................................................................................................................................................................... 15 6 Abbreviations ........................................................................................................................................................................ 16 2 1 INTRODUCTION HSPA+ was introduced in 3GPP Rel.7 and is a combination of HSDPA (3GPP Rel.5) and HSUPA (3GPP Rel.6). HSPA+ is a further enhancement of HSPA that introduces higher order modulation and MIMO, CPC, carrier aggregation, Layer-2 enhancements, architecture improvements in the uplink and downlink. With each new 3GPP release, the improvements and new features added to HSPA+ improve the uplink and downlink speed, reduce the latency and increase number of simultaneous data connections that can be supported. In the next section, the background is presented followed by HSPA+ features and their impact on the performance, followed by conclusion. 2 BACKGROUND There is continuous thrust to improve data rates in both uplink and downlink in mobile telecom networks. In second generation or 2G, the main thrust was on circuit switched voice calls while circuit switched data services were provided at 9.6kbps. Internet services like web browsing are inherently bursty and did not optimally use the dedicated bandwidth and also, billing was done on the basis of minutes and not on the basis of data volume. GPRS, a software upgrade from GSM, offered the first always-on data connection which supported bursty data traffic at 171 kbps maximum in the downlink. Next was EDGE or Enhanced Data-rates for GSM Evolution which was conceived as an easy way for operators of GSM networks to squeeze more performance from the network. Meanwhile, ITU specified the technical requirements for third generation technology while also stipulating that compatible technologies should offer smooth migration paths from 2G networks. To that end, UMTS rose to the top as the 3G choice for GSM operators. UMTS or Universal Mobile Telecommunication System which is based on WCDMA technology was fixed in Release-99 of 3GPP and published in 2000. It was the next step after GSM/GPRS/EDGE and supported improved voice and data services with 5MHz bandwidth. UMTS Rel-99 was initially conceived as a circuit switched based system and was not well suited to IP packet based data traffic. Once the basic UMTS system was released and deployed, the need for better packet data capability became clear, especially with the rapidly increasing trend towards Internet style packet data services which are particularly bursty in nature. The initial response to this was the development and introduction of HSDPA (3GPP Release 5), followed by HSUPA (3GPP Release 6) to provide the combined HSPA service. With growing demand from the industry for even higher data rates, increased spectral efficiency and reduced latency HSPA evolved with each 3GPP Release from Release-7 onwards. For operators that have already deployed HSPA, HSPA+ is a preferred to way to protect existing investment and provide high data rates before moving onto LTE. 2.1 HSDPA (RELEASE-5) HSDPA (High Speed Downlink Packet Access) is an upgrade to UMTS/WCDMA with improvements to the downlink only, providing peak theoretical data rates of up to 14.4Mbps. 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 delay-sensitive business applications such as Virtual Private Networks (VPNs). High Speed Downlink Packet Access is predominately a software upgrade to Release 99 of the UMTS standard. HSDPA usually requires only new software and base station channel cards, instead of necessitating 1 the replacement of major pieces of infrastructure from UMTS and does not require additional spectrum for deployment. As a result, UMTS operators could deploy HSDPA quickly and cost-effectively. HSDPA provides peak theoretical data rates of up to 14.4Mbps in downlink and it achieves its performance gain through following radio features: a) High speed shared channel b) Reduced transmission time interval (TTI)~2ms which allows the NodeB to respond to changing radio conditions quickly and allows faster scheduling c) Fast Hybrid Automatic Repeat Request- which improves the efficiency of error processing and is implemented in Node B as compared to RNC for faster response. 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. While these worked 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 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 packet-data connections. 2.2 HSUPA (RELEASE-6): HSUPA (High Speed Uplink Packet Access), standardized in Release 6, constitutes a set of improvements to the uplink only, that optimizes uplink performance using the Enhanced Dedicated Channel (E-DCH). These improvements include higher throughputs, reduced latency, and increased spectral efficiency. HSUPA provides peak uplink data rate of 5.76Mbps. For applications like VoIP, improvements balance the capacity of the uplink with the capacity of the downlink. HSUPA achieves its performance gains through the following approaches: a) An enhanced dedicated physical channel in the uplink b) A short TTI, as low as 2 msec, which allows faster responses to changing radio conditions and error conditions. c) Fast Node B-based scheduling, which allows the base station to efficiently allocate radio resources. d) Fast Hybrid ARQ, which improves the efficiency of error processing and is implemented in Node B as compared to RNC for faster response. The combination of TTI, fast scheduling, and Fast Hybrid ARQ also serves to reduce latency, which can benefit many applications as much as improved throughput. HSUPA can operate with or without HSDPA in the downlink, although it is likely that most networks will use the two approaches together. Beyond throughput