 | Issue: | Asia-Pacific III 2009 |
| Article no.: | 4 | |
| Topic: | LTE and the software defined radio | |
| Author: | Xiaodong Zhu | |
| Title: | CTO, Western Europe Marketing Platform | |
| Organisation: | ZTE | |
| PDF size: | 239KB |
About author
Xiaodong Zhu is the CTO of ZTE’s Western Europe Marketing Platform. Mr Zhu began his career at ZTE’s Shanghai R&D centre. Mr Zhu left ZTE to work for Conexant as the General Manager of Conexant Wireless Communication (Shanghai) division, which later became Skyworks Wireless Communication. Mr Zhu also served Broadcom (Shanghai) as a General Manager prior to returning to ZTE in his current position. Xiaodong Zhu earned his masters in Electrical Engineering from Zhejiang University.
Article abstract
As wireless networks evolve, operators will have to integrate several technologies – legacy with advanced – into a single network. Operators must also choose their new networks whilst trying to maintain compatibility with future standards not yet available in the market. This is a particular challenge in developed markets, where mobile operators are faced with radio infrastructure lifecycles of a few years, making it difficult to achieve return on investment. Software defined radio offers a way to minimise risks and costs.
Full Article
The mobile telecom industry is facing new challenges with the rapid growth of data traffic. Today, more than 100 million subscribers worldwide benefit from mobile broadband services delivered over 300 networks. According to Informa, global mobile data revenues will increase 77 per cent from 2007 to 2012 while global mobile data traffic will grow far faster, increasing more than 1,000 per cent over the same period. Driven by the booming of mobile Internet, the forecast increase in network traffic is leading operators to new strategies such as spectrum re-farming and launching potentially lower-cost systems. Wireless networks are evolving, integrating several technologies into a single network. During this process, multiple technologies will co-exist. In some cases, an operator will maintain three networks at the same time (2G, 3G and LTE) while a national LTE network is rolled-out. Traditionally that has not been possible, as moving onto a next-gen network would require vast investments from a carrier. That is no longer the case. Software defined radio (SDR) technology enables network upgrade and evolution by software configuration, removing the need to invest in new replacement hardware. Flagship network operators, including Hong Kong CSL, are proving that SDR can increasingly save costs in the network and are acting as pioneers for SDR. This article explores the benefits provided by SDR technology and the case study of CSL. The potential of SDR technology The basic principle behind SDR technology is to create an open, standard, modular, programmable hardware platform, on which new radio station functions can be realised by installing the corresponding software modules. On the universal platform, modification and extension of the radio station functions are done by modifying the software, with no need to redesign the hardware circuit (or very limited hardware upgrades), greatly improving the interconnect with existing or future radio stations. Traditional network infrastructure causes many problems on the long run. For example, product development is usually version specific within a specific standard. When a new technology or a new version appears and new services are offered, new chips have to be developed for the new generation equipment. Consequently, this can restrict the application of new technology and services, or demand greater investments by operators and, as well, cause inconvenience for subscribers. The increasing varieties of standards call for greater frequency resources and make frequency allocation and management more difficult. The production of multi-frequency and multi-mode handsets is also becoming more difficult and increasingly costly. SDR provides a solution to these problems. SDR offers a universal radio communication platform, based on which new services can be delivered and new technology can be used just by updating the software. This substantially reduces development costs and cycles and enables existing products to keep up with the development of technology. SDR-based products have a longer product lifecycle compared with traditional products and can combine two or three different standards in one product, translating into less investment risk. Meanwhile, their standardised hardware makes production easy. Thus, manufacturers will benefit much more from producing SDR-based products than from traditional ones. The evolution of different technologies leads operators into a maze – how to deal with the uncertain network development? Mobile network convergence faces many challenges like coexistence of multiple standards, configuring capacities for different standards, reducing TCO while operating 2G, 3G or B3G networks, and securing service continuity for subscribers. Confronted with these problems, operators find it hard to work out a successful investment strategy. For operators, construction of a mobile network requires large investments and involves significant risks. By deploying SDR, operators can reduce the risks. From the end-user’s perspective, future SDR-based technology can also provide subscribers with a universal terminal platform that supports most international standards. SDR-based terminal equipment can also be upgraded with software to support new standards, helping users achieve real international roaming and obtain new services. SDR should benefit the entire industrial value chain from technical research and development, to equipment manufacturers, telecom operators and end-users, so it is drawing much attention from the telecom industry. The evolution from hardware defined to software-defined communications is the third revolution in wireless communications field – after the move from analogue to digital and from fixed to mobile. CSL case study Established in 1983, CSL, with more than 2.65 million subscribers, is one of the leading mobile operators in Hong Kong and aims to provide them a cutting-edge user experience. CSL was the first mobile company in Hong Kong to launch GPRS services in 2000, and also the first to deploy EDGE technology in 2003. At the end of 2005, CSL acquired the Hong Kong-based operator NWM, and became the largest mobile operator in Hong Kong. The new company inherited four original networks of the former two companies, namely, one GSM900 network, two GSM1800 networks and one UMTS2100 network. The main objective of the acquisition was to achieve economies of scale and cost reductions and to achieve a stronger competitive edge. However, the four dual mode networks with three frequency bands hindered CSL’s further development. The two GSM1800 networks had high maintenance costs. The 3G data services of existing networks provided only 1.8Mbps downlink data rates and could not support software upgrades. Higher downlink data rates would need large investments in infrastructure. Implementing network convergence and evolution would be particularly challenging due to the coexistence of multiple modes and frequency bands. To solve this problem, CSL selected a converged network solution based on a SDR platform to reconstruct the four networks into a single network and enable future upgrades. The biggest difference between SDR and conventional base stations is that the Radio Remote Unit (RRU) of the former can be software programmable to implement intelligent spectrum allocation and support various systems including GSM/WCDMA/LTE. The Baseband Unit (BBU) is based on a unified MicroTCA (standardised architecture circuit board) platform and offers a compact format, low power consumption, standard modules and strong scalability, and it can process various GSM/WCDMA/LTE baseband signals. A single 2G/3G convergence network was proposed to replace the original four networks and to implement unified management. The convergence network could also support HSPA+ through software upgrade and the evolution to LTE at low cost. Many skyscrapers and a dense population in Hong Kong resulted in a complicated wireless environment; reconstructing the 2G/3G network under such circumstances was a challenging task. Due to the sheltering and isolation of high-rise buildings, multi-directional antenna coverage is required in many areas. To ensure good coverage, multiple RRUs were deployed to provide independent RF signals and power amplification for each direction. Moreover, multiple RRU cells were combined into one logical cell, greatly reducing handoffs in certain areas and effectively improving service experience of terminal users. Due to the complexity of the existing network structure of CSL, many sites had antennas of different modes, which were replaced by high-performance multi-band antenna (900/1,800/2,100MHz tri-band antenna). The application of high-performance multi-band antennas not only ensured good coverage, but also facilitated the subsequent network cutover. Moreover, it helped CSL greatly reduce Operation and Maintenance (O&M) costs. As CSL leased the IP network for most of the transition between the base stations and the Radio Network Controller, the network management system was also customised by adding two functions: QoS (quality of service) monitoring of the third party’s IP network and remote management of Network Elements (NEs) via VPN (virtual private network). By using the NEs’ existing functions and newly added performance management and alarm management functions, the QoS of IP transmission network can be effectively monitored. Network management over VPN also guarantees security of management data and saves rentals of the IP network as the NEs only occupy private IP addresses. The CSL network convergence project was a challenging and complicated undertaking as it involved replacement of all existing network devices. CSL worked closely with its suppliers to make a detailed implementation plan. A special project team consisting of over 300 engineers and technical professionals was responsible for execution, monitoring and management of the project. Recently, CSL announced an LTE commercial trial network in Hong Kong based on its SDR network. It will also deploy UMTS900, which is the first instance of spectrum re-farming seen in Hong Kong. In a joint event in September, the operator demonstrated live the new LTE technology in action, achieving peak download speeds in excess of 100 Mbps. The growing number of access technologies and air interfaces mean that mobile operators are faced with the daunting task of choosing current networks and at the same time maintaining compatibility with future standards not yet available in the market. This is a particular challenge in developed markets, where mobile operators are faced with radio infrastructure lifecycles of a few years, making it difficult to achieve return on investment. SDR is an efficient way of minimising risk and costs. According to Dimitris Mavrakis of Informa, “SDR presents a new concept for mobile operators and allows them to have a simpler, more efficient network and in many cases, a guaranteed evolution path to future technologies.” CSL pioneered the use of this technology with the development of a convergent network in Hong Kong and the commitment to upgrade to LTE. Many other leading operators will soon follow suit.
