White Paper EEvvoollvviinngg mmiiccrroowwaavvee mmoobbiillee bbaacckkhhaauull ffoorr nneexxtt--ggeenneerraattiioonn nneettwwoorrkkss February 2008, NEC Corporation Executive summary service, e-mail, and Internet access. Now, many operators are starting to provide new broadband The arrival of mobile broadband services requires a step data services such as multimedia content downloading, mobile increase in the capacity of mobile backhaul networks, TV broadcasting, on-line games, and ubiquitous computing. particularly microwave radio transmission networks. These Industry and market forecasts anticipate that data revenue will services require a new type of backhaul solution, one that scales grow at an accelerating rate with this broader spread of for the future and enables the delivery of a multitude of mobile broadband data services. services. Such a solution will present several challenges to any As the provision of broadband data services expands, it takes microwave network. more and more of the available bandwidth, which is the same • Carrying multi-service traffic over microwave links issues that afflicted fixed network operators for several years. cost-effectively Operators are thus expected to steadily expand their network • Increasing transport bandwidth capacity for data services capacity by implementing new mobile access technologies, such where possible as HSxPA, WiMAX, LTE, and UMB, to provide a stress-free • Maximizing efficiency of bandwidth utilization where connectivity environment for their subscribers. possible Figure 1 shows a roadmap of service availability based on the • Providing carrier-grade manageability and survivability of implementation of mobile access technologies. In addition to the multi-service transport widespread provision of 2G/3G services, 3.5G HSDPA commercial services have already been launched in a number of NEC, the world’s leading supplier of microwave radio systems, countries. Mobile WiMAX services are also available, and many now provides mobile network operators with a future-proof operators are preparing for their deployment. LTE and UMB Hybrid Packet Radio solution comprising PASOLINK series services are expected to be deployed starting in 2009. All of these microwave radio and CX2200 series multi-service transport new services will basically be provided on packet-based gateway equipment. This solution supports a flexible mixture of platforms instead of the TDM/ATM ones used for current TDM and packet traffic and is suitable for both transitional 2G/3G-based services. Thus, mobile systems will be gradually phase and the long term. It also provides advanced switched to packet-based platforms over the next several years. functionalities, including adaptive modulation radio (AMR), Packet-based services flexible traffic aggregation, intelligent QoS, and powerful OAM. TDM-based services 3GPP-LTE 3GPP2-UMB In this way, this Hybrid Packet Radio solution achieves backhaul network evolution strategies that will lead to future Mobile WiMAX revenue growth. 3G(IP)/HSUPA 3G(ATM)/HSDPA Mobile backhaul trends 2G 2008 2010 2015 Mobile infrastructure has been widely implemented over the Figure 1. Roadmap of service availability past 10 years, and operators have grown their businesses by providing 2G/3G voice and data services for short message To provide broadband data services, operators need to expand 1 the capacity of their backhaul. As a large number of links for provide the switching capacity to be flexibly apportioned to tens of thousands of wireless base stations is required, we must TDM/ATM and packet traffic in accordance with their traffic consider how transmission networks can evolve cost-effectively. volumes. Furthermore, current investments in widely So far, leased lines and microwave radio links are traditionally installed microwave equipment should be protected even as used for such networks. Microwave radio systems have been the type of traffic changes due to service transition and widely deployed due to their economical equipment cost, easy migration. installation, and disaster resiliency. Figure 2 shows an example In the switching and multiplexing of TDM/ATM and packet of a mobile backhaul network in which microwave equipment is traffic, service level agreements (SLAs) should be satisfied. used for the transmission network. For example, voice services are delay-sensitive but not so Microwave sensitive to packet loss, while mobile TV broadcasting E1 Radio BSC Optical Network services are bandwidth and packet-loss sensitive but not so BTS STM-1 sensitive to delay. These differences in sensitivity mean that a finely tuned SLA guarantee mechanism should be applied. STM-1 E1 Node-B RNC 2) Increasing transport bandwidth capacity for data services Figure 2. Example of mobile backhaul architecture In 3G and later microwave-based backhauls, the link bandwidth capacity needed to accommodate broadband data Now, almost 90% of mobile operators have deployed services, such as HSDPA, is expected to grow drastically. The microwave systems, and the diffusion ratio has reached 60% of most effective way to expand the link capacity is to widen the base station coverage. Microwave systems have obviously frequency band of the carriers. However, operators assigned a assumed an important role in the evolution of mobile systems. limited frequency band need to maximize the usage efficiency of the given spectrum. The microwave links for 2G/3G Requirements for microwave mobile backhaul services are engineered to guarantee the bandwidth even under the worst weather conditions. In contrast, for later new Microwave-based backhaul needs to evolve as the new data services, such as HSDPA, it is more important and mobile systems are widely implemented. However, operators desirable to maximize throughput in accordance with the also need to ensure the continuity of their existing 2G/3G weather conditions, while ensuring the high-quality traffic services. For example, current 2G services will be provided until (e.g. 2G/3G-based voice traffic). This requires the application at least 2015, so the transition and migration to packet-based of adaptive modulation schemes that can dynamically backhaul has to be done in a cost-effective and quality-assured maximize the spectrum efficiency under the given weather manner. Therefore, microwave equipment needs to provide a conditions. multi-service platform that can accommodate TDM, ATM, and other packet traffic such as Ethernet, MPLS, and IP 3) Maximizing efficiency of bandwidth utilization simultaneously as well as maintain the existing 2G/3G service Another way to expand capacity is to apply effective quality. multiplexing schemes. There are two approaches to Four functional capabilities are required to support such a multiplexing: overhead reduction and traffic aggregation. microwave-based backhaul evolution. In the overhead reduction scheme, higher throughput is obtained by eliminating unnecessary bits of data. For 1) Carrying multi-service traffic cost-effectively example, encapsulating TDM/ATM traffic in IP and/or In line with the expected service availability illustrated in Fig. Ethernet protocols adds several tens of bytes of overhead to 1, a multi-service platform is needed that can dynamically the native TDM/ATM traffic. This degrades effective work as a TDM platform, a TDM/packet hybrid platform, and throughput. If the TDM/ATM traffic is still dominant, this an all-packet platform. It should thus support both overhead should be eliminated where possible. TDM/packet hybrid switching and effective multiplexing. In In the aggregation scheme, higher throughput is obtained addition, to enable smooth and seamless migration, it should through the statistical multiplexing effect. Since burst traffic 2 can impact SLA compliance in over-subscribed environments, TDM traffic and effective packet switching for Ethernet, technologies that guarantee SLA compliance should also be MPLS, and IP. Various interfaces such as TDM E1/T1 to applied. STM-1, ATM E1/T1 IMA to STM-1, and Fast Ethernet to Gigabit Ethernet can be accommodated and reconfigured by 4) Providing carrier-grade manageability and survivability simply changing the interface modules. The equipment can With both TDM/ATM- and packet-based platforms, thus be used as a TDM/ATM backhaul platform, a TDM/ATM comprehensive management functionality is needed to and packet hybrid platform, and a pure packet platform as ensure smooth transition and migration. Packet-based the mix of services provided evolves. management functionality has historically been less than In addition, all types of traffic can be mapped onto the same satisfactory, while TDM/ATM-based management radio interface, meaning that, once an outdoor unit is functionality has proven capabilities. Furthermore, installed, it can continue to be used during the performance measurement functionality, such as transition/migration process. measurement of transmission delay and jitter, is required for These flexibilities provide mobile operators with a solution maintaining and verifying compliance with multiple SLAs. that overcomes migration and upgrade issues with a Therefore, an advanced OAM functionality is required for the minimum-cost. packet-based backhaul scenario. From a network reliability point of view, packet-based 2) Adaptive modulation radio (AMR) backhaul networks also require resiliency against link and/or PASOLINK’s AMR functionality enables link capacity to be node failures, which is equivalent to or better than optimized in accordance with the weather