Vanu® software radio is the first wireless infrastructure solution that enables individual base stations to simultaneously operate GSM, CDMA, iDEN and beyond. With wireless standards developed entirely in software instead of specialized, single-purpose hardware, the Vanu Anywave ® solution accelerates time-to-market for new services while delivering unprecedented capital and operating cost-savings. Carriers can easily and economically add new wireless standards or increase system capacity via remote software downloads. Anywave software can also accommodate a full range of RF hardware configurations that deliver customized coverage for indoor, outdoor and mobile cell site requirements. With Vanu's software radio, it's Anywave… anywhere.
The Vanu Anywave® radio access network (RAN) is an integrated suite of products and technologies that spans from the antenna site to the telecom switch interface. At the core of the Anywave RAN is innovative Vanu Software Radio technology incorporated into the base station.
Vanu software radio is the most complete realization of the software radio vision anywhere in industry. The software that implements radio communications standards – including the high speed signal processing functions for the air interface – is simply a collection of portable applications that run on a high-volume server or any PC board. The radio front end is standards-neutral and can support multiple channels at the same time.
The Vanu software radio approach of portable software on standard hardware provides powerful technical benefits, including the following.
- Vanu systems naturally support multiple wireless standards (GSM, CDMA, iDEN, etc), in the same way that an IT server runs multiple and different applications. Processing capacity can be dynamically shared between wireless standards as the mix of subscriber loading changes.
- Each operator can select the hardware platform ideal for their application, across a wide range of capacity, size, power consumption, redundancy, environmental ruggedness, and cost options. The entire range of standard server, blade, and embedded platforms is available for consideration.
- The performance per unit cost of Vanu systems continually improves over time, tracking the improvements provided by the Moore's Law curve of the high-volume computer industry.
- Managing a deployed Vanu system is cost-effective because mature, sophisticated and affordable management technologies are available that were developed for remote lights-out operation of server farms. Trained staff experienced with these tools are also widely available.
Challenges and Solutions
Implementing a full communications standard as portable software on standard PC hardware is not easy – at least if high performance is required. Vanu, Inc. has developed an effective approach over 10 years of research and development. Here are some of the challenges and solutions that we have uncovered over time:
Existing middleware approaches fail to provide the necessary performance, so the modularity necessary for software reliability and reuse is difficult to achieve.
Vanu has developed its own middleware, Sprockit™, specifically designed for high speed signal processing. Sprockit exploits the special features of signal processing software, such as unidirectional mono-typed data flows, to reduce overhead costs. It also focuses on critical issues at the intersection between high performance and portability, such as optimizing to different data cache sizes without rewriting any software modules.
Existing signal processing algorithms perform poorly when implemented in a naïve fashion on general purpose processors (GPPs) such as the x86 and PowerPC families. Processor architecture features are radically different on GPPs than on the processors for which existing algorithms were developed. For example a memory load that causes a data cache miss can be one hundred times more expensive than a multiple-accumulate operation (MAC), while a tight loop with each iteration depending on the previous one can run slowly due to microarchitecture pipeline issues.
Vanu, Inc. draws on a fundamental understanding of communications theory and processor architecture issues to develop new algorithms that perform well in the GPP context. Some examples of this are a replacement for the Viterbi decoder (U.S. patent #7,139,967) and a Walsh code decoder (patent pending).
Existing system designs perform poorly when executed on a platform with moderate or higher jitter. On a standard PC or server, jitter arises at multiple levels: data and instruction cache misses, PCI bus access contention, operating system interrupts, and contention for the processor among multiple applications.
Vanu software radio places the tight timing requirement needed for modern wireless standards on the radio front end. The front end time stamps incoming samples before sending them to the signal processing software. When the software generates data samples for transmission, it labels the samples with a timestamp and sends them to the radio head. The radio head holds the samples until that time is reached then delivers them to the D/A converter for transmission. Based on this approach, Vanu systems can hit tight transmission windows whose width is much smaller than the jitter of the platform where the software executes.
Decoupling Vanu software from real-time in this way has significant added benefits. Portability is much better than the tightly-timed software of most base stations on the market today, since the relative cost of different software components normally changes when moving to a new processor or board. At the same time, Vanu systems are able to exploit novel signal processing algorithms that offer improved performance in exchange for more variability of processing cost per sample or frame.
Software Radio vs Firmware Radio
The technology adopted by the rest of the industry to implement software radio is best called firmware radio. This is used by virtually every traditional cellular base station equipment manufacturer. Firmware radio approaches exploit low-level non-portable software. Examples include VHDL or Verilog for FPGAs and hand-written assembly code for DSPs. Even software written in C often results in firmware radio. The C code may be hand-optimized for specific chip architectures, partitioned into software modules to specifically match the capability of different CPUs and buses on a board, or designed around specific hardware acceleration functionality provided at the system-on-a-chip (SOC) or board level.
The firmware radio approach results in hardware lock-in. Because the wireless standard's software cannot be reused when the hardware is upgraded, and is too expensive to rewrite from scratch, the manufacturer is forced to continue using the same hardware design even as Moore's Law improvements rapidly render it obsolete. As a result, the system delivered to the end user is higher cost, higher power consumption, and larger size than it needs to be.
Vanu Software Radio overcomes the problems of firmware radio through creative design approaches that provide a high level of software portability. As a result it delivers the full performance and cost benefits of Moore's Law component improvements to end users.
To understand the Vanu Anywave® radio access network (RAN), it helps to look at the system from two points of view: 1) at the system level and 2) inside the base station itself.
Systems Level Architecture
At the highest systems level, the Anywave RAN looks the same as any other base station subsystem (Fig 1). It spans from the switch interface at one end to the antenna at the other, including a base station controller (BSC), data link backhaul network, the base station itself (BTS), and RF support components such as a power amplifier and duplexer.
Looking in more detail at the systems level architecture shows the key differences from legacy base station system designs that give the Anywave RAN its compelling advantages.
The Anywave RAN uses high-volume industry-standard equipment, which provides excellent cost effectiveness and offers a superb range of hardware and feature options. The BTS and BSC execute on standard servers such as IBM, Intel, HP or Dell. The IP backhaul network uses standard networking equipment such as Cisco or HP. The customer can select the equipment that best meets their requirements, whether it is the most cost-effective IT grade equipment, NEBS-compliant systems, or rugged devices for challenging underdeveloped countries and military environments.
Software and Protocols
The Anywave RAN uses open industry-standard protocols such as IP and software platforms such as Linux throughout, providing significant reductions in operations and maintenance cost.
The Anywave RAN is native IP throughout for signalling, voice, data, and management. Any desired backhaul links can be used (e.g. T1/E1, Ethernet, satellite, microwave). Because IP is used throughout the Anywave RAN, cost-effective commercial switches, bridges and routers are available, as well as tools for network monitoring and maintenance. The burst-like data traffic characteristic of 2.5G and 3G cellular standards can be efficiently multiplexed over IP, allowing for OPEX reductions in backhaul from the BTS not possible with traditional designs.
The Anywave RAN connects to the customer's mobile switch (MSC). Multiple switch interfaces are available that gateway the IP based Anywave RAN to legacy switch interfaces such as SS7, GSM A or CDMA IOS. The Anywave BSC interfaces directly to advanced soft-switches. For military, government and PBX applications, a SIP interface to standard VOIP switches is also supported.
Upward and Downward Scalability
The Anywave RAN uses mature, cost-effective and reliable "server-farm" data center designs for scalable capacity. The BTS and the BSC are structured as multiple blades or servers interconnected by high-speed ethernet. Within a single BTS or BSC, the blades or servers are integrated by off-the-shelf widely-used software subsystems that provide efficient load-balancing and reliability services up to very large system scales. This design supports not just large nationwide cellular deployments but innovative home access points (BTSs) femtocells devices where a single BSC may need to support tens of thousands of BTSs. On the other hand, because all Anywave components execute in the same standard software environment, a "network-in-a-box" solution is supported for low capacity systems, which is particularly useful for rural operators or disaster recovery emergencies. The entire Anywave RAN can run on a single server, including BTS, BSC and a VOIP switch.
Base Station Architecture
The base station is the core component of the Anywave BSS. Based on Vanu Software Radio technology, its architecture differs significantly from other traditional and SDR base stations.
The base station consists of one or more servers or chassis blades connected to one or more RF heads depending on cell sectorization and/or the number of different frequency bands deployed in the BTS (Fig 2) . A range of RF heads manufactured by Vanu partners cost-effectively meet a wide array of user needs ranging from high power macrocells to low-cost indoor picocells, and from multi-carrier multi-standard sites to single-carrier single-standard sites.
Normally there is one RF head per band licensed by the operator. For example, an operator with just cellular spectrum will use a single RF head, while an operator with cellular (800/900MHz) and PCS (1800/1900MHz) spectrum will use two. Each server or blade simultaneously supports multiple channels and/or wireless standards (eg, GSM, CDMA, etc). The number of servers is determined by the desired maximum traffic volume.
The Anywave multi-carrier BTS architecture also avoids the RF combining network used by the line card architecture characteristic of other traditional and SDR base stations (Fig 3). This saves significant power on transmit and improves sensitivity on receive.
The functionality of the Anywave BTS is carefully divided between the processing server and the RF head for maximum flexibility and cost-effectiveness (Fig 4). All the functions specific to a particular wireless standard are implemented using portable Anywave software on the processing server. The RF head is standards-neutral, with all features such as channel bandwidth and frequency hopping controlled remotely by the server software. Multiple servers can connect to a single RF head with each server processing a different set of RF channels. A single server can support channels of different wireless standards simultaneously.
The link between the processing server and RF head naturally extends over long distances to support distributed antenna systems in situations where this is desirable (Fig 5).
The Anywave RF head exchanges digitized samples representing the band or channels of operation with the processing server over a standards-based RF sample interconnect. Different RF head vendors use different RF sample interconnects. At present, both direct fiber links and Gigabit Ethernet (GigE) are supported. As industry-standard RF sample interconnects such as Open Base Station Architecture Initiative Reference Point 3 (OBSAI RP3) become more prevalent, Vanu will add support for these standards in the Anywave BSS product line.
The Gigabit Ethernet RF sample interconnect highlights the advantages of using a standard networking technology to interface to the RF head. The GigE protocol is supported directly by most industry-standard servers, eliminating the need for interface boards to connect RF heads to servers. GigE also supports switching, which improves redundancy and permits reallocation of BTS servers across antennas in response to changing loads.
A typical Anywave RF head supports up to 16 carriers, depending on the cellular standards being used. This design can, in many cases, provide significant heat dissipation and power loss savings compared to the power-inefficient combining networks used in legacy line card BTS architectures.
The analog electronics in the RF head offers sufficient linearity and spurious free dynamic range (SFDR) to support any of a variety of cellular standards. Selectable carrier frequency and bandwidth allows multiple carriers in different wireless standards to operate simultaneously (Fig 6), for example, the transmission and reception of GSM and CDMA channels at the same time through the same RF head. The carriers in use can even be changed dynamically, for instance to match the capacity of each standard to the number of customers currently in the coverage area of the BTS. The transceiver in the RF head performs digital channelization and down-conversion on receive and digital up-conversion and summing on transmit to reduce the bandwidth requirements on the RF sample interconnect.
The Vanu Anywave Base Station Subsystem brings together a suite of technologies that together provide an unprecedented level of flexibility, scalability and cost-effectiveness to cellular operators. The core Vanu Software Radio technology enables true simultaneous, multi-standard operation and takes advantage of industry-standard servers, reducing a wireless operator's CAPEX and OPEX while significantly reducing requirements for on-site maintenance. The use of advanced multi-carrier RF heads supports multi-standard operation and dynamic capacity reallocation. A switched-fabric standard networking protocol in the fronthaul also makes distributed antenna solutions economical. IP everywhere in the backhaul and switch connection enables the use of commodity equipment and multiplexed network links.
These benefits are the direct consequences of Vanu's unique, software-centric approach to the radio access network. The multi-standard software can run on any of a wide range of server platforms and exploit any of a range of backhaul, fronthaul, and RF head equipment, all based around industry-standard, commercially available platforms and networking protocols. Consequently, with the Anywave RAN, network operators can focus infrastructure investments on system configurations that meet their specific requirements for features and coverage scalability at minimal cost. Moreover, operators can significantly enhance business model flexibility through remote software downloads from a central location and on-demand spectrum and capacity allocation. Vanu Anywave networks in both macrocell and innovative vehicle pico cell, enterprise in-building, and home deployments enjoy significant cost and flexibility advantages over conventional infrastructure alternatives.