Gearing up for 3G growth

By Guillaume Pertinant, ST Microelectronics

Introduction

After a decade of hype, 3G networks have finally taken off. 2005 saw widespread deployments of data-centric wireless services, with the total number of 3G subscribers reaching 55 million at the end of last year.* Carriers are focusing their efforts on new wireless data and video services to increase their revenue streams and grow market share. To keep pace with growing demands for wireless data, telecom operators will continue to invest in the deployments of next-generation cellular technologies and expand coverage of data-centric networks.

Data-centric revolution, together with the emergence of diverse networking standards, such as EDGE, CDMA2000, W-CDMA, and WiMAX, has stepped up the need for greater throughput, performance, and flexibility in cellular base-station designs. Infrastructure equipment manufacturers are looking at ways to protect their hardware and software investment by deploying cost-effective and flexible solutions that support multiple standards, provide maximum re-usability, and offer future-proof upgrade paths.

Existing base-station designs are mostly based on discrete DSP and FPGA implementations or proprietary ASIC architectures. As a result, network equipment manufacturers have had to choose between the benefits of integration - low component count, low cost, inherent high reliability - and flexibility, which enables fast development of products' derivatives or upgrades, while reducing the NRE and manufacturing costs.

Market's first baseband modem SoC

The market's first System-on-Chip (SoC) solution for signal-processing in wireless infrastructure applications, the STW51000 from STMicroelectronics, changes the name of the game. With its unparalleled combination of on-chip integration, system modularity, and multi-standard support, ST's baseband modem device represents a major initiative to shrink costs and increase performance and flexibility in the fast-growing and highly competitive wireless infrastructure market.

ST's STW51000 is a super-integrated and highly modular device that combines two DSP cores with a standard ARM RISC processor core, 16 Mbit of embedded SRAM memory, and dedicated co-processors for all major wireless standards on a single chip. This unique approach reduces the footprint and BOM (Bill-of-Materials) of discrete solutions by up to 75%, with no trade-off in performance and flexibility.

A single device offers up to 1.2 GHz of DSP core performance and 300 MHz of ARM processing power, equaling a total speed of 29,000 MOPS (Million Operations Per Second) and 7,500 MIPS (Million Instructions Per Second). PHY and lower MAC benchmarks have shown that the STW51000 delivers an unsurpassed voice and data channel density - at the industry's lowest cost-per-channel: Two chips can handle as many as 16 HSDPA (High-Speed Downlink Packet Access) users sharing a 14.4-Mbps throughput, while a single-device implementation can address up to two-carrier GSM/EDGE.

The embedded digital signal processor (DSP) core is a quad-multiplier/accumulator (MAC) engine designed to meet the massive signal-processing needs of high-end telecom applications. Its innovative architecture combines VLIW and RISC features to achieve the optimal balance between performance and size. Both DSP cores inside the STW51000 run only the signal processing tasks, and thus no DSP cycles are wasted to execute the control tasks. The ARM926 core acts as the SoC controller, handling all control tasks such as protocol stacks, memory management, RTOS, and drivers.

The device embeds two hardware accelerators for voice and data error correction, dedicated to the channel-decoding tasks, defined in the 3GPP and 3GPP2 specifications. Supported standards include 2/2.5G and 3G (W-CDMA, CDMA2000, TD-SCDMA), as well as WiMAX. Both the Turbo Decoder Engine (TDE) and the Convolutional Decoder Engine (CDE) are tightly coupled to the on-chip direct memory access (DMA) to accelerate the data transfer.

Fabricated in ST's 130nm high-performance CMOS technology, the advanced modular architecture of the STW51000 can be easily and quickly customized with the addition or removal of peripherals or logic blocks to match the needs of a specific application.

The platform modularity goes hand in hand with comprehensive software support. The device comes complete with a full set of in-house software libraries, enabling OEMs, for the first time, to implement modems for all major wireless standards from a single source.

With designs based on the market's first baseband modem SoC, ST's STW51000, equipment manufacturers can use a single platform for many different applications, saving development time and costs in new designs, as well as allowing existing products to be upgraded quickly and efficiently.

Turnkey solutions for today's and tomorrow's networks

Being at the heart of the 3G business model, significant take-up of enhanced data services unlocks lucrative revenue streams to network carriers and their equipment suppliers. At the same time, these new opportunities bring new challenges. One of them is to find a cost-effective solution to delivering increased capacity and improved coverage in areas of high user density.

With the arrival of 3G services, even a relatively small number of high-speed data users can consume all the available resources of the nearest macro-cell base station. It will become extremely difficult for operators to provide sufficient user capacity and coverage using conventional outdoor base station cell sites. Recent industry research also suggests that as much as 70 per cent of subscribers will be located indoors - inside office buildings, college campuses, subways, airports etc. - when accessing wireless broadband applications.

In-building deployments of pico-cells (mini cellular base stations with ranges up to 200 meters) are set to play a major role in designing high-speed mobile data networks, reducing the cost of infrastructure and macro-cell site acquisition. ST's turnkey solution for pico base stations combines superior performance and physical parameters of the SoC baseband processor with optimized software modem libraries, including the latest releases of WCDMA, HSDPA (High-Speed Downlink Packet Access) and HSUPA (High-Speed Uplink Packet Access). With its unparalleled chip-level integration, ST's baseband modem offering meets critical size, power and cost constraints of pico-cell base-station designs.

The emerging global standard for broadband wireless access, WiMAX/IEEE 802.16 (Worldwide Interoperability for Microwave Access) already provides an attractive option for carriers looking to expand their broadband coverage into less densely populated areas or to backhaul their existing wireless and wireline networks. In the longer term, WiMAX has the potential to be adopted by wireless carriers as a 4G data-centric technology, equaling the cell reach of current 3G technologies and exceeding their bandwidth capability.

A new momentum started to build for WiMAX at the end of 2005, after the IEEE ratified the new ‘mobile WiMAX' standard. The 802.16e specification ushers in a seamless, nomadic phase of WiMAX, where base stations can communicate with moving devices, allowing users to move around and maintain their broadband connection. Industry analysts expect there will be more than 50 million WiMAX subscribers by 2010, with the worldwide sales of WiMAX equipment growing at a CAGR of 140% to reach US$3.5 billion at the end of the decade.

STMicroelectronics offers a comprehensive solution for Mobile WiMAX base stations. Its modem software portfolio includes 802.16e software for FDD (Frequency-Division-Duplex) and TDD modes, developed in-house and optimized for ST's baseband modem SoC. 802.16e benchmarks have shown that a single STW51000 can address a complete 10MHz TDD (Time-Division-Duplexing) PHY running on the DSPs, as well as the lower part of the MAC running on the ARM926. This one-of-the-kind package opens a fast and cost-effective path to next-generation mobile broadband services, shortcutting cost and power concerns of discrete DSP and FPGA implementations, while increasing the integration and performance level.

Conclusions:

A super-integrated, reconfigurable signal-processing platform with multi-standard support is a key to successful deployment of new data-centric cellular infrastructures. ST's all-in-one offering for network equipment manufacturers benefits from the Company's world-class IP portfolio, leading-edge semiconductor processes, and extensive volume manufacturing capability, combined with the dedication and support of a focused Wireless Infrastructure organization. The group closely follows the latest industry developments and plays an active part in major standardization initiatives (3GPP, WiMAX Forum). Its strong product roadmap ensures continuity and future-proof upgrade paths towards flexible and powerful baseband-processing platforms for next-generation wireless broadband networks.