Emerging Mobile-Network Architectures are Raising Demand for High-Speed Optical Interconnects.

How moving baseband processing away from the antenna can help.

Demand for mobile Internet access continues to grow massively, aided by factors such as the increasing affordability of smartphones and services such as 4G Advanced that deliver real-world data rates capable of supporting seamless video streaming experiences while on the move. More than half of all IP traffic is expected to originate from non-PC devices, such as 3G and 4G mobiles, by 2019.

Mobile network architectures are adapting and reorganizing to support data services that demand massive throughput and instant response.

In addition to smartphone-related growth, the success of the mobile Internet is also linked with the emergence of new types of connected devices, including wearables such as smartwatches and personal wellness monitors, as well as the Internet of Things (IoT). The combined effects are revolutionizing almost every aspect of people’s personal and professional lives, changing working patterns and home or leisure activities, streamlining access to services, enabling smart infrastructures, and expanding channels for social interaction.

Changing Demands on Mobile Infrastructures

Wireless infrastructures continue to change in response to dramatic shifts in the activities and consumption patterns of mobile subscribers. Whereas early infrastructures provided relatively simple connectivity linking predominantly voice traffic into the carrier network, today’s subscriber demands call for high-speed, high-bandwidth connections for accessing data services like file storage and social-media or business applications. Consumers want to manage their personal content and share their stories anytime and from anywhere, while business users are becoming increasingly reliant on Software as a Service (SaaS), delivered to the mobile, to accomplish their daily tasks. As a result, networks are changing to position computing and storage closer to subscribers. These assets need to be connected using efficient, high-speed optical data links throughout the infrastructure from the backbone to the antennas.

Fiber to the Antenna

Moving baseband processing away from the antenna permits smaller and lower-cost cell sites and also helps the network to operate more efficiently. Fiber-to-the-Antenna (FttA) connections can enable this baseband processing to be located up to several kilometers away from the Remote Radio Head (RRH), using transceivers that support standard communications protocols such as the Common Public Radio Interface (CPRI). Moreover, baseband processing can be done on standard server hardware, which reduces the development and deployment costs of the baseband functions. Standard server hardware also makes it easier to deploy software updates and to more easily scale capacity. Also, the use of standard servers gives extra flexibility to move some services and content closer to consumers, maximizing efficiency and supporting new features and revenue sources. Figure 1 shows how centralized servers and baseband processing are connected optically to RRH sites and the network backbone.

Figure 1: High-speed optical connections are essential to achieve flexible network architectures.

Figure 1: High-speed optical connections are essential to achieve flexible network architectures.

In today’s 4G networks, radio access is provided through a diversity of cell types, including micro, pico and femtocells to “fill in” coverage between macro cell sites, as illustrated in Figure 2. The smaller cells can cover various types of localities, such as a city block or a shopping complex down to an area as small as a single building. These heterogeneous cells combine both the radio front-end and the baseband back-end functions in an integrated and small footprint. In fact, the footprint requirements are so small that they can be easily deployed on a rooftop or within a building’s existing service cabinet. This type of architecture effectively reduces reliance on expensive macro-cells and enables operators to increase coverage and quickly implement additional capacity in targeted areas as needed.

Smaller coverage areas need not use high-speed fiber to connect to the network, but will provide additional traffic that needs to be consolidated and connected to a fiber-optic backbone. These consolidation points could use a centralized server as a convenient source of needed connectivity, processing power and storage. Any cloud-based applications located on the centralized server could also be provided to small-cell users, further leveraging the installed infrastructure.

Figure 2: Heterogeneous network with connections to fiber backbone.

Figure 2: Heterogeneous network with connections to fiber backbone.

Bringing Cloud Computing to the Core

Efficiently connecting the radio access points to the network edge is just one aspect of the creation of a network capable of satisfying end-user demand for mobile Internet services, which is simultaneously growing and intensifying. Today’s users expect their services and content to follow them wherever they may be on the network. Techniques such as virtualization or software-defined networking are increasingly attractive to mobile network operators, to achieve greater flexibility and ensure always-optimal service delivery.

At the physical layer, virtualization calls for high-speed, high-efficiency optical connections among the switches, servers, routers and storage that make up the network. High-speed optical backbone connections are already well established, leveraging transceiver modules capable of communicating at gigabit data rates such as OC-192 over distances of several kilometers. However, connectivity inside today’s data centers is increasingly reliant on pluggable optical modules. These range from modules designed to support connectivity across PCBs and backplanes over distances of a few centimeters to connections between racks or servers that require communication ranges of up to several meters.

Because modules designed to communicate at high speeds over long distances tend to be more complex and expensive, and consume more power, than modules for shorter-range connections, a variety of different module types is being developed to satisfy the different connectivity demands at the board, backplane, rack and data-center levels. Accordingly, suppliers of optical transceivers, such as Finisar, have a wide variety of modules optimized for use over various communication distances and capable of supporting a number of high-speed communication standards such as 10G, 40G and 100G Ethernet.

Optical modules that support CPRI, like the example from Finisar shown on the left side of Figure 3, will be used between the RRH and centralized baseband servers. Speeds in the 1-gigabit-per-second range will typically be sufficient for these applications. Centralized servers will use higher speed modules to connect to the optical fiber backbone of the outside mesh, perhaps using 10G Ethernet modules like the example from Finisar shown in the middle of Figure 3. Speeds in the 10 to 40-gigabit range will typically be found in these areas. Emerging backbone applications that aggregate the heaviest communications traffic will use even higher bandwidth modules, such as the 100 Gigabit Ethernet module from Finisar shown on the right side of Figure 3. Future generations of 200G and 400G products for communication distances from a few meters up to about 10km are now being developed.

Figure 3: Optical modules address a wide range of distance and data-rate requirements in today’s data centers.

Figure 3: Optical modules address a wide range of distance and data-rate requirements in today’s data centers.

On the other hand, system-level interconnects can now be accomplished using optical engines such as the 10G BOA Board-mount Optical Assembly (Figure 4), which is designed to be placed close to the host ASIC and communicate over multimode-fiber ribbon cable. These parallel transceivers boost connectivity performance in storage, data and high-performance computing applications, ensuring high signal integrity and low power consumption. The 10G BOA is available with 12 full-duplex channels or 24 separate transmitters and receivers and supports multirate capability from 1Gbit/s to 10.5Gbit/s per channel.

Figure 4: Board-mount transceivers extend optical connections throughout the system.

Figure 4: Board-mount transceivers extend optical connections throughout the system.


Mobile network architectures are adapting and reorganizing to support data services that demand massive throughput and instant response. Less centralized and more distributed than previous generations, and interconnected on every level using optimized, high-bandwidth optical links, today’s networks are increasingly Cloud-like in terms of their performance, efficiency and flexibility.


Photo-RudyRamos_webRudy Ramos is the Project Manager for the Technical Content Marketing team at Mouser Electronics, accountable for the timely delivery of the Application and Technology sites from concept to completion. He has 30 years of experience working with electromechanical systems, manufacturing processes, military hardware, and managing domestic and international technical projects. He holds an MBA from Keller Graduate School of Management with a concentration in Project Management. Prior to Mouser, he worked for National Semiconductor and Texas Instruments. Ramos may be reached at rudy.ramos@mouser.com