RTC Magazine

The 4G wireless revolution is making significant market advances with major deployments worldwide. On the heels of this explosive growth in new service deployments is the opportunity for equipment manufacturers to develop smaller Long Term Evolutions (LTE) or WiMAX solutions for specific applications, such as deploying in developing nations, rural deployments, public safety, smart power grids, military, prisons, universities and more. Savvy manufacturers and service providers who get to market quickly with a fully functional and scalable system will have the competitive advantage. Using complete, pre-integrated LTE Evolved Packet Core and WiMAX ASN gateway solutions, equipment manufacturers can get to market more quickly and incur minimal development costs. Based on MicroTCA platforms, they can deliver solutions that are carrier-class, cost-effective, scalable, flexible and standards-based with the ability to be custom branded.

With the demand for wireless broadband for mobile users, the LTE and WiMAX standards groups established several objectives intended to support bandwidth intensive applications such as video and online games, and to reliably deliver services such as interactive location-based services (LBS). The major objectives include increased data rates, greater flexibility and simplified network architecture. The target for true 4G is data throughputs of 1 Gbit/s. Real-world data rates will vary based on numerous factors.  For LTE, peak data rates support 100 Mbit/s for downloads and 50 Mbit/s for uploads. LTE Advanced, scheduled for release in 2011, will support 1 Gbit/s. For WiMAX, the mobile 802.16e standard delivers data rates as high as 40 Mbit/s, while the upcoming 802.16m standard is targeting 1 Gbit/s.

Service providers deploying networks in different regions around the world are looking for greater flexibility of spectrum usage. The radio spectrum for LTE ranges from 1.25 MHz to 20 MHz, and for WiMAX the spectrum ranges from 2 GHz to 66 GHz, the most common being 3.5 GHz.

To simplify the network architecture, it is designed as a pure IP-based architecture, eliminating legacy protocols, such as GPRS, and providing simpler compatibility to IMS networks and interoperability between WiMAX and LTE. The three main categories of equipment that LTE and WiMAX bring to the wireless network are: 1) the User Equipment (UE) or Customer Premise Equipment (CPE), 2) the Radio Access equipment also called Base Stations or enodeB (for LTE), and 3) the Core Gateways, which provide multiple control and data services. 

Other objectives include reduced latency for establishing connections and transmission, plug and play operation and lower operating costs. There is a push to achieve seamless mobility. For LTE this includes support for different radio-access technologies such as GSM, UMTS and CDMA2000.

Applications Where MicroTCA Makes Sense

It is important to note that when describing gateways, one size does not fit all. Many of the early deployments have been targeted to large cities where the service providers can maximize revenue per deployment. ATCA systems with large banks of processors can provide the scale for these large deployments. But as service providers start to target the large numbers of mid-size cities, smaller towns and rural locations, the CAPEX rules change, and MicroTCA becomes a more cost-effective option. In addition, there are other smaller applications that open the door to good revenue-generating opportunities. 

In the examples below, it is imperative that the gateway be designed as a highly reliable system architecture that can be dropped into locations that may be less than hospitable. They must be easily serviceable, remotely manageable, and must be scalable to add more processing power when the subscriber count increases. 1U MicroTCA-based systems with support for up to six AMC processors running carrier-grade Linux, and gateway application software with full standby failover, meet these requirements. In fact, MicroTCA systems are already deployed as WiMAX gateways and are on trial for LTE EPC test environments. AMCs offer a right-sized granularity for these types of deployments, where the population count is not as dense as in large metropolitan cities.

Developing Nations: Developing regions around the world are rapidly deploying mobile data services, including areas that have never had communications infrastructure in the past. Strong demand by consumers and competitive conditions by service providers are accelerating frequency spectrum auctions. Brazil’s telecom regulator, ANATEL, has recently designated the 2.5 GHZ band to support nationwide deployment of a neutral wireless broadband. Because of its neutrality, it can support either LTE or WIMAX deployments. The intent of these governments is to facilitate rapid economic development via broadband Internet access. Mobile data services in Latin America are expected to grow at a CAGR of 31 percent rate from 2010 to 2015, according to Pyramid Research. 

Rural Deployments: The American Recovery and Reinvestment Act (ARRA) of 2009, included $2.5 billion to increase the availability of broadband in rural areas of the U.S. This opens the doors for tier-2 and tier-3 service providers to install wireless networks and run a profitable business. Similar to developing nations, there are remote regions where the subscriber count is small to moderate—anywhere from tens to hundreds of users—and these communities have never had broadband service in the past. Setting up and maintaining wired broadband such as DSL or cable is cost-prohibitive when service providers consider the infrastructure investments in setting up copper or fiber lines to the “last-mile” and setting up the backhaul network from the ISP to the Internet, or “middle-mile.” And since the per capita income in rural households tends to be lower than urban incomes, wireless base stations and gateways provide a cost-effective alternative. 

Smart Power Grids: Another part of ARRA includes a $3.4 billion funding for 100 smart power grid projects. Each country has different definitions for smart grids (SGs). SGs provide a more efficient means to deliver power from suppliers to consumers with reduced costs, energy saving policies (such as time-of-usage) and higher reliability. Either WiMAX or LTE can be used to interconnect the utilities. Besides standard networking, these systems can integrate control systems and security. 

Public Safety: In 2007, the Federal Communications Commission adopted the 700 MHz Band for public safety services. The objective is to establish a nationwide broadband communications network that provides interoperable services for state and local public safety users. Specifically, the public safety bands are 763-775 MHz and 793-805 MHz, with commercial allocation in between. Light weight but carrier-grade systems provide the means to move these systems into locations that require emergency services, and once again MicroTCA systems provide the high availability and right size for the level of subscribers on this network. 

System Level Considerations

When one considers the main functions of an LTE or WiMAX network, they typically think of the base station and the core gateways. Figure 1 shows an LTE network and Figure 2 shows a WiMAX network. However, the Element Management System (EMS), which monitors and manages these systems, is also a key component. And lastly, since LTE is a completely IP-centric technology, there will be a large push for Voice-over-LTE, or VoLTE, which will accelerate the demand for IMS (IP Multimedia Subsystems) with SIP-based services. MicroTCA-based systems are very well suited for all these services. Utilizing a common MicroTCA and Linux-based processing architecture across all these functions reduces the need to develop on and support disparate platforms. It also reduces time-to-market, and avoids much of the cost to stock spare equipment.

Figure 1
LTE Network.

Figure 2
WiMAX Network.

Gateways can be comprised of the MicroTCA platform, x86-based processor AMCs, and Carrier Grade Linux. Along with third party WiMAX ASN or LTE gateway software, a complete, fully-functional gateway can be developed. 

Base stations can be developed comprised of the MicroTCA platform, including support for Serial RapidIO or PCI-e options, along with x86-offs. These systems include GPS-based synchronization timing modules complying with Telcordia’s Spectrum 3 requirements, and they support oven-controlled oscillators for reliable hold-over in the absence of a reference clock. There are third-party AMCs on the market that provide the radio-frequency, baseband and control elements integrated on a single AMC card for Layer 1, 2 and 3 LTE-based and WiMAX-based base station solutions.

Integral to both LTE and WiMAX, an Element Management System (EMS) consists of the systems and applications related to managing one or more physical devices that make up a system. It allows these nodes or network elements to be managed in a unified way using one management system, rather than in a distributed, more cumbersome manner. Known as FCAPS, the key functionalities include managing faults, configurations, accounting, performance and security. In addition, Session Initiation Protocol (SIP)-based servers deliver cost-effective, feature-rich, enhanced next-generation network (NGN) services. Based on a pure IP implementation, new service offerings can be quickly developed and readily deployed, network-wide, on IMS-enabled, converged VoIP and TDM/IP networks. 

Details on the LTE EPC Gateway Solution

Evolved Packet Core (EPC) is a set of functionalities that comprises the core of an LTE network. The eNodeBs will access these functions to determine how to behave when a user equipment (UE), such as a mobile phone, initiates a service request of the network. The goal of LTE from the EPC perspective is to simplify and better organize the services and functions of the network to reduced CAPEX and OPEX as well as provide higher bandwidth, higher spectral efficiency and lower latency than existing 2G/3G technologies.

The three major components to LTE’s EPC are the mobility management entity (MME), serving gateway (SGW) and packet data network gateway (PGW). Since LTE is completely a packet-based network, all communications to and from the EPC will be native IP packet-based and leverage existing commodity infrastructure and simplify configuration and operations. There are well defined interface specifications for communicating between EPC components, thereby reducing interoperability issues between multiple vendor products.

The MME’s main function (Figure 3) is to manage subscriber session control plane functionality, which uses the S1-C (C is for control plane) interface to communicate through the eNodeB to the UE. Authentication, authorization, ciphering and security key management are all dealt with by the MME. The S6 interface is used to communicate with the home subscriber server (HSS) database to manage authorization and accounting. Activating and deactivating as well as assigning an SGW to a UE, tracking the UE, and transitioning roaming handovers is within the MME’s responsibility in the EPC. The MME uses the S11 interface to inform the SGW of the session details. MME provides for intercept of signaling. To be compatible with 2G/3G networks, the MME provides control plane management with SGSN service from those architectures via the S3 interface. External interfaces supported by this solution include S1-MME, S11, S6a, S10, S13, S101, S102, S3 and SGs. 

The SGW’s main function (Figure 4) is to receive and route all UE packet data and serve as a mobility anchor for UEs transitioning between eNodeBs. The SGW uses the S5 interface to route data packets to a PGW within the same core network and will adhere to the S8 interface specifications when routing to a different network’s PGW such as in the case of a roaming UE. The S1-U (U is for User plane) interface is used between eNodeB and SGW to carry the user traffic and is subject to latency restrictions. Intercept traffic capture and replication is a function within the SGW. To be compatible with 2G/3G networks, the SGW provides user plane access with SGSN service from those architectures via the S4 interface.

The PGW’s main function (Figure 4) is to route data packets from the SGW to external services such as the Internet, IP multimedia systems (IMS), or Public Switch Telephone Network (PSTN). Between the SGW and PGW are S5 for inter-network and S8 for other network traffic. Acting as the mobility anchor for other non-LTE-based networks is a key role for the PGW. The PGW performs packet filtering, policy enforcement and interception, charging support and packet screening. 

The feature set supported by the SGW/PGW solution includes online and offline charging, static and dynamic QoS, default and dedicated bearers, and SGi interface based on local DHCP, RADIUS and DIAMETER. External interfaces supported include S11, Transparent SGi, Non-transparent SGi, S5, Gn, Gx, Gy/Ro, Gz/Rf and S4. The solution can scale to support up to one million subscribers.

Figure 5 shows how the processors are configured into the MicroTCA platform to provide fully functional LTE EPC gateway systems with standby redundancy. A maximum configuration with four data processors and a standby can deliver an aggregate throughput of 3 Gbit/s with current generation AMC processors. With average per-subscriber data rates of 0.5 Mbit/s, this system can support up to 6,000 active subscribers. The modular architecture allows scaling of data processors to support smaller numbers of active subscribers, thus minimizing the cost. Scaling down also allows the integration of MME functions into the same system.

Equipment manufacturers who are looking for turn-key LTE EPC or WiMAX ASN gateway applications to get to market quickly with low development costs can leverage these solutions. They are developed to be comprehensive, ready-for-market solutions that are right-sized and cost-effective for numerous wireless broadband applications. Comparatively, the scale of AdvancedTCA-based solutions is too large and they are too expensive to compete in many of these markets. MicroTCA systems cover the gamut of LTE and WiMAX applications from the base stations, gateways, Element Management and IMS. 

Performance Technologies
Rochester, NY.
(585) 256-0200.
[www.pt.com].