 | Issue: | Europe I 2009 |
| Article no.: | 9 | |
| Topic: | LTE ready backhaul | |
| Author: | Aviv Ronai | |
| Title: | Chief Marketing Officer | |
| Organisation: | Ceragon Networks | |
| PDF size: | 219KB |
About author
Aviv Ronai is the Chief Marketing Officer of Ceragon Networks; he has over 15 years of experience in the telecommunications industry. Prior to joining Ceragon, Mr Ronai held several senior marketing positions at ECI Telecom, most recently as Vice President of Marketing and Communications. Prior to joining ECI Telecom, Mr Ronai served in the Israeli Air Force as a telecommunication officer and held several project management positions. Aviv Ronai holds a Bachelor’s degree in Electrical and Electronics Engineering and a Master’s Degree in Business Administration from Tel-Aviv University.
Article abstract
Commercial LTE deployments will begin during 2010. As LTE access is deployed, it will be important to prepare the backhaul networks to support high-speed/high bandwidth transmission between cell sites and the operator’s core network. LTE-ready backhaul means high capacity, low latency and support for an all-IP architecture. Of the three backhaul technology options operators can choose from, wireless point-to-point microwave can deliver the best cost-performance, with faster ROI driving forward the proliferation of advanced mobile services in the LTE era.
Full Article
Long Term Evolution (LTE) the new standard for air interface for wireless handhelds, is the current ‘buzz’ in the mobile corridors. As its name suggests, LTE is likely to attract much interest for a very long time. While the media likes to focus on LTE access networks, and more specifically on spectrum allocation for the new LTE services, it is also important to look at the evolution of the mobile backhaul network – the network that will carry the increasing broadband traffic. The backhaul network connects the mobile access network – the mobile phones and the cellular base station – to the core, or backbone, of the network. Of the three main backhaul transport technologies – fibre, copper and wireless point-to-point microwave – the latter is perhaps the most important to look at. Used in over 50 per cent of all mobile backhaul deployments worldwide and nearly 70 per cent outside the USA, point-to-point microwave systems offer simple and cost efficient backhauling for voice and high-speed data services. Point-to-point microwave supports higher data rates than copper T1/E1 lines, and easily overcomes the high cost and limited availability associated with fibre. Backhaul for LTE For most mobile users, LTE is not likely to have much impact any time soon. This is mainly because LTE, like 3G, focuses on technology rather than on applications. Over the next few years, the user will continue to rely on 3G and, in some regions, on 2G technology. The direction of the market however is clear. As consumers get more and more accustomed to new services and applications that drive their ‘bandwidth appetites’ upwards, even today’s most advanced 3G networks will eventually become obsolete. Because of the growing demand for bandwidth, LTE is already part of the mobile operator’s game plan. Operators have to learn the technology and its impact on their networks, applications and service offerings. In particular, operators will have to prepare their backhaul networks to handle the coming LTE launches planned to start in 2010. LTE defined Third Generation Partnership Project Long Term Evolution (3GPP LTE) is the name given to a project within the 3GPP to improve the UMTS mobile phone standard. LTE provides mobile operators with an evolutionary path for the delivery of faster data speeds and new services. LTE utilises new radio access technology optimized for IP-based traffic and offers operators a simple upgrade path from 3G networks. Mobile network broadband evolution Backhaul systems designed to serve LTE deployments should address three basic requirements: 1. higher capacities – backhaul should be able scale to 100Mbps or beyond 2. lower latencies – solutions that support extremely low latency, ten milliseconds end-to-end, are needed 3. all IP – Support IP traffic from the get-go Figure 1 below describes the evolution of mobile access network capacity up to LTE. Next generation wireless backhaul solutions will achieve these systems. Figure 1: 3G and LTE Capacity & Latency Requirements The backhaul challenge Higher capacities and lower latencies are necessary for LTE backhaul. So is the ability to support IP traffic and all-IP architectures, since LTE networks will be used mostly to deliver data rather than voice. Since today’s backhaul networks are still dominated by TDM – be it T1/E1 lines or high-capacity SDH/SONET – one main consideration operators are faced with today is how to migrate their networks to IP. From legacy to IP To make the migration process as painless as possible, backhaul networks will continue to support legacy services in the foreseeable future. The migration to IP does not necessarily mean that current investments in transport equipment will be lost. On the contrary, good migration strategies will cap new investments in legacy-only equipment, and deliver new services over high capacity IP-enabled equipment. A good migration strategy will maintain critical services using trusted legacy technology, while gradually shifting revenue generating services to the new packet network. During the migration process, delivering Ethernet over existing TDM networks can also be considered as an interim solution. In the end, however, these systems will encounter scaling issues and encapsulating Ethernet over TDM adds latency instead of decreasing it. Flexible backhaul systems, on the other hand, allow the operator to use either legacy or Ethernet – or both – in accordance with its specific needs. The hybrid solutions depicted in Figure 2 below, support native TDM and native Ethernet simultaneously. Thus, operators can connect TDM ports today, and gradually shift traffic to Ethernet ports in the future. This shift can be done remotely, so no additional CAPEX or OPEX is entailed. Figure 2: Native/Hybrid Approach to support both Legacy and Ethernet over a single radio The industry has already established that the end game for next generation mobile backhaul networks is all-IP/Ethernet. Ethernet is not only more scalable, it also offers huge cost savings across the entire network value chain. For example, using the same spectrum, antenna size and peripheral equipment to backhaul native Ethernet packets over point-to-point microwave delivers between 25 per cent and 60 per cent more bits compared to similar TDM based systems. LTE-ready backhaul LTE traffic will be dominated by data applications ranging from non-real time services such as email exchange, web browsing, peer-to-peer and file sharing to real-time and delay sensitive services such as video and voice. In addition to delivering high capacity and low latency over an IP network LTE-ready wireless backhaul systems also need to support: Quality of Service with ACM (Adaptive Coding and Modulation) – As a great deal of the LTE traffic will be data, it will use much of the network’s resources, but its contribution to revenue will not be proportionate to data usage. Cost-per-bit must therefore be optimised to transmit more bits for any gives spectrum, antenna size and transmitter power. Broadband backhaul strategies can be applied to carry extensive data traffic, assigning different availability classes to different types of service over a single radio link. This will allow more efficient planning of link capacity for best-case scenarios rather than for worst case as is done today. Voice and real-time video applications will continue to enjoy ‘five nines’ (99.999 per cent) availability, while non-real-time data packets can settle for four or even three nines, with little or no discernable impact upon the user’s experience. By using ACM with prioritised data to ensure the constant flow of high priority bits at all time and to allow additional capacity most of the time, the overall radio capacity can be maximised at no extra cost. The table below shows how ACM can even reduce costs by using smaller antennas to deliver equivalent prioritized capacity. Figure 3: Point-to-Point Microwave Systems, with and without ACM Statistical multiplexing Unlike TDM based transport technologies, Ethernet gives operators the ability to use statistical multiplexing. Statistical multiplexing is especially important in ‘aggregation backhaul’ applications; it helps optimise traffic management over the network, reduce congestion and helps operators get more out of their networking investment. Ethernet rings using IP/MPLS, PBT or Carrier Ethernet The shift to packet-based networks makes it easier to use Ethernet rings; this improves availability and increases capacity. Depending on the overall network strategy – whether it is IP/MPLS, PBT, ITU G.8031/2 path protection or just an enhancement of xSTP – operators can consider the complexity and cost, and apply an appropriate solution for each network segment. Integrated Carrier Grade Ethernet switches as part of the radio link An additional switch at the site may come in handy to increase port count, for demarcation purposes, and to up-sell additional services and for traffic management. An integrated switch will also serve cell sites with limited real estate by eliminating the need for additional external devices. Commercial LTE deployments should begin sometime in 2010. As LTE is deployed for access, it will be important to prepare the backhaul networks that will support high-speed/high bandwidth transmission between cell sites and the operator’s core. LTE-ready backhaul means high capacity, low latency and support for an all-IP architecture. Of the three backhaul technology options operators can choose from, wireless point-to-point microwave can deliver the best cost-performance features, bringing faster ROI and driving forward the proliferation of advanced mobile services in the LTE era.
