Comparing WiMAX and HSPA+ White Paper

Comparing WiMAX and HSPA+ White Paper

Introduction HSPA+ or HSPA Evolved is the next step in the 3GPP evolution. With 3GPP Rel-7 and Rel-8, several new features are added to this 3G WCDMA technology, including enhancements to increase peak and average sector throughput. By incorporating higher order modulation, MIMO and multi-carrier capability, HSPA peak rate performance more closely matches that of WiMAX Forum Release-1 products that have been commercially available since 2008. Despite these improvements, HSPA+ is still a CDMA-based technology whereas WiMAX Forum Release-1, with an all-ip architecture and OFDMA, represents a next generation solution for broadband mobile networks. Although DL peak rates are comparable, other technology distinctions set WiMAX Forum Release-1 apart from HSPA+ for the delivery of value-added broadband services. For today s operators with WCDMA networks, HSPA+ offers a cost-effective and graceful migration path to achieve higher channel throughput while WiMAX offers the opportunity for operators to migrate to a next generation broadband network that is built with an open architecture to allow new innovation for applications and devices. HSPA+ or HSPA Evolved: What is it? 3GPP Rel-7 and 3GPP Rel-8 HSPA+ also know as HSPA Evolved is a further evolution of WCDMA and is defined by 3GPP Rel-7 and 3GPP Rel-8. Key enhancements in 3GPP Rel-7 include: Downlink: º º Modulation up to 64QAM with (1x2) SIMO supported º º (2x2) MIMO is supported with 16QAM Uplink: º º Modulation up to 16QAM supported with 64QAM as an option The above enhancements are projected 1 to provide a theoretical peak DL sector rate of 21 Mbps for 64QAM with (1x2) SIMO and 28 Mbps with 16QAM and (2x2) MIMO. The theoretical peak UL sector rate with 16QAM is reported to be 11 Mbps. These reported rates assume no coding. Other Rel-7 features improve the VoIP capacity. 3GPP Rel-8 enables simultaneous support for 64QAM and (2x2) MIMO for a further improvement in the peak DL sector rate to 42 Mbps, again this assumes no coding. Rel-8 also introduces Dual Cell HSPA (DC-HSPA) a capability that enables the aggregation of two adjacent 5 MHz carriers. DC-HSPA is only supported for (1x2) SIMO but gives WCDMA operators who happen to have contiguous licenses to achieve a higher DL peak sector rate without implementing the more costly base station antenna upgrade from (1x2) SIMO to (2x2) MIMO. DC-HSPA does not impact the UL data rate as it still operates on a single 5 MHz carrier. The Significance of Peak Rates and Forward Error Correction: Peak rates for HSPA are typically quoted with no coding. This does not represent a realistic deployment scenario. WiMAX reports peak rates with 5/6 coding for 64QAM and 3/4 coding for 16QAM. In a typical deployment peak rates with this level of coding would be available to users in close proximity to the base station where they would experience good propagation path conditions. For a uniform distribution of users throughout the cell coverage area, 10 to 20% of the users may have access to these propagation conditions with the above coding. 1 Bergman, Gerstenberger, Gunnarsson, and Strom; Continued HSPA Evolution of Mobile Broadband, Ericsson Review 1/2009 1

These HSPA enhancements compared to 3GPP Rel-6 are summarized in the following table. Parameter HSPA HSPA + or HSPA Evolved 3GPP Rel-6 3GPP Rel-7 3GPP Rel-8 Duplex FDD FDD FDD Channel BW 2x5 MHz 2x5 MHz 2x5 MHz 2x10 MHz DL Modulation 16QAM 64QAM 16QAM 64QAM 64QAM BS Antenna (1x2) SIMO (1x2) SIMO (2x2) MIMO (2x2) MIMO (1x2) SIMO UL Modulation QPSK 16QAM 16QAM 16QAM 16QAM Table 1: Key 3GPP Enhancements for HSPA Comparing WiMAX and HSPA+ Peak Rate Comparisons In Figure 1 a comparison of peak rates for HSPA+ with paired 5 MHz channels is shown in comparison to WiMAX Forum Release-1. For a 1 to 1 comparison with WiMAX, the HSPA+ numbers are shown for a code rate of 5/6 and 3/4 for 64QAM and 16QAM respectively. The WiMAX peak values are for a TDD implementation with a 10 MHz channel BW. The WiMAX peak values are shown for a range of DL to UL traffic ratios to show the range of peak rates attainable in a typical deployment scenario. In the DL, the peak rates between HSPA Rel-8 and WiMAX are similar as would be expected, with each having the capability of supporting 64QAM with (2x2) MIMO. The uplink channel peak rate for WiMAX is higher due to the support for uplink two-user collaborative spatial multiplexing which enables the uplink traffic from two separate users to be combined. The peak rate for DC-HSPA was not included in the chart. It, of course, has the same DL performance as HSPA Rel-8 with 64QAM and (2x2) MIMO but since it requires twice as much spectrum it has half DL peak spectral efficiency. 50 45 40 35 30 25 20 15 10 5 0 DL UL Figure 1: Peak Rate Comparison 2

Other Technology Distinctions With a physical layer based on scalable OFDMA and an all-ip core network, WiMAX technology was optimized for the delivery of broadband data services in a fixed, nomadic, or mobile environment. With DSL and cablelike performance, WiMAX provides operators the opportunity to offer differentiated, value-added services not attainable with 3G networks. Alternatively, CDMA-based HSPA has evolved from a network designed and optimized specifically for mobile voice services. Although HSPA+ and WiMAX have several attributes in common including; adaptive modulation and coding, fast scheduling, hybrid ARQ, and bandwidth efficient hand-off; there are a number of important differences that make WiMAX with OFDMA the clear choice for next generation broadband networks. These differences include 2 : Scalable channel BW: WiMAX currently supports channel BW of 5, 7, 8.75 and 10 MHz and can optionally support channel bandwidths up to 20 MHz. High tolerance to self-interference and multipath: With OFDMA, the orthogonal nature of the subchannels assures a high tolerance to interference in a non-line-of-sight (NLOS) environment without the need for complex equalizers. Frequency selective scheduling: This WiMAX attribute enables sub-channel allocations based on propagation conditions to specific users thus assuring each user is getting the maximum attainable signal level. Fractional frequency reuse: The use of sub-channels can be adaptively optimized over the cell coverage area to mitigate the potential for interference at sector boundaries and at the cell edge to enable deployments with aggressive frequency reuse. Orthogonal uplink multiple access: OFDMA in the uplink assures minimal multiple access interference. This provides WiMAX with higher uplink channel throughput. Quality of Service (QoS): As opposed to a priority-based approach as used in 3G systems, WiMAX uses a connection oriented technique to dynamically manage QoS in both the DL and UL directions to support a wide range of real time and non real time services. Supported services range from simple file transfers and Best Effort web browsing services to latency-sensitive real time gaming and VoIP services. Open All-IP network architecture: HSPA+ is evolving from a legacy, multi-layered 3G circuit-switched network. Alternatively, WiMAX is based on an open all-ip flat end-to-end architecture. The ability to use a common network core without the necessity to support packet and circuit-switched network elements results in simpler protocols for data flow and lower network costs. Furthermore the WiMAX network when deployed as an overlay, has the ability to interwork with existing networks. Another important distinction between these technologies is time-to-market. Although 3G WCDMA systems are field-proven, having been in place for several years, the HSPA Rel-7 upgrade has only recently become commercially available and 3GPP Rel-8 enhancements are not expected until 2010. OFDM-based WiMAX systems have been deployed since 2006 and WiMAX Forum Release-1 TDD products, based on OFDMA, for portable and mobile broadband applications have been commercially available since 2008. While HSPA+ may be a viable upgrade path for many WCDMA operators, WiMAX Forum Release-1 provides an upgrade alternative that goes beyond what HSPA+ can provide and gives operators a time-to-market advantage in getting to the next level of broadband performance with a next generation network. 2 For a discussion of these differences with additional technical detail see Mobile WiMAX Part II: A Comparative Analysis, June 2006, available on the WiMAX Forum website. 3

WiMAX Forum Release-1: Coming Attractions New Features Planned for WiMAX Forum Release-1 WiMAX Forum Release-1 is based on the IEEE 802.16e-2005 air interface standard, but the initial Release-1 profiles adopted by the WiMAX Forum for certification represent only a subset of the features supported by the IEEE standard. Recently the WiMAX Forum has adopted additional 802.16e-2005 features as well as additional frequency profiles for WiMAX Forum Release-1. Some of these enhancements and features will directly impact channel or sector throughput and peak rate performance. Upcoming WiMAX Forum Release-1 products are expected to feature the following enhancements: Frequency Division Duplex (FDD and H-FDD): This will enable greater deployment flexibility for operators with paired spectrum assignments. Additional frequency profiles including the 700 MHz band: With lower path and building penetration loss, the lower frequency bands will greatly improve the economics for deployments in rural areas. 20 MHz channel BW in selected frequency bands: Larger channel BW leads to a lower cost per megabit for deployments in regions with high population density where data capacity is the key metric of interest. 64QAM in the uplink (this is currently an optional feature): 64QAM in the UL provides a 50% UL channel peak and throughput increase. Adjacent Multi-Carrier (AMC) permutation: This permutation provides enhanced sub-channel utilization in low mobility situations to improve channel throughput by approximately 25%. Alvarion is currently a recognized worldwide leader in the WiMAX market with over 250 WiMAX deployments in more than 100 countries and a product portfolio to cost-effectively address the varied deployment challenges faced by operators. Alvarion is also one of the founders of the WiMAX Forum and has, over the years, continued to be a proactive participant in the WiMAX Forum s activities. As a key contributor to the Forum s Technical Working Group, Alvarion has played a major role in defining the features and capabilities that are integrated into WiMAX Forum Release-1. The WiMAX Forum s extensive ecosystem comprising over 500 member organizations, representing all elements in the supply chain, promotes certification to enable interoperability and compliance testing as WiMAX Forum Release-1 technology continues to evolve. 4

Conclusion WiMAX offers a new open network business and deployment model that is vastly different than the traditional 3GPP model. It allows operators to build a broadband Internet infrastructure that is all-ip end-to-end with open network architecture. The success of HSPA in the marketplace shows that demand for mobile broadband will only increase in the future. HSPA family of technologies are still CDMA-based and tied to the constraints of a legacy circuit-switched network architecture, originally optimized for voice services. HSPA+ will provide some of today s WCDMA operators a viable upgrade path to increase channel peak rates and throughput. WiMAX on the other hand, will give today s mobile operators the opportunity to build a next generation all-ip network that is lower in cost and is built with an open architecture to enable new innovation for applications and devices. WiMAX provides mobile operators an opportunity to leverage a different ecosystem for broadband data applications, as they look to introduce new services to their customers. With its focus on embedded devices, WiMAX will continue to evolve with further performance enhancements to enable the delivery of DSL and cable-like broadband services over a mobile network. Alvarion s leading position in the WiMAX market and the ability to deliver complete, end-to-end turnkey solutions will enable its continued market leadership. 5

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