The explosion in data rates is driving a need for more base stations, which are typically big, expensive pieces of equipment. Integrating 4G functions into Systems-on-Chip designed to reduce the size and expense of a Compact Base Transceiver Station enables wider deployment to meet the growing data traffic demand.
Operators are experiencing the early effects of the mobile data traffic explosion. While most of the initial data volume was driven by mobile data cards in laptops and Web tablets, the growing percentage of smartphone subscribers is beginning to add significant demand.
From 2008 to 2010 mobile data traffic volume in the United States is expected to grow from 138 petabytes to the staggering amount of 1 exabyte (1018 bytes), nearly an increase of 750 percent. As subscriber usage models go, mobile data consumption tends to follow wire-line broadband usage models within a few years of delay, giving wireless radio access technology a chance to catch up.
Experts predict this trend to continue, with even moderate forecasts leading to an annual U.S. mobile data traffic volume of about 40 exabytes by 2014 and 90 exabytes by 2015 (see Figure 1). This amounts to a growth of roughly 9,000 percent within just five years. So how will this explosion in data traffic affect the mobile radio infrastructure equipment market?
Data capacity from 4G technology
With LTE (R8) and LTE Advanced (R10), radio access technology will be evolving from Single Input Single Output (SISO) to Multiple Input Multiple Output (MIMO), applying 2×2 transmit and receive diversity, and soon to Multi-User MIMO (MU-MIMO), applying 4×4 RF diversity. This can yield a capacity increase of about 200-300 percent across an entire cell area. With new spectrum assets released by auctions globally, operators in 2015 can expect to utilize roughly 40 MHz of paired spectrum, a capacity increase of another 400 percent.
Using today’s 3G deployments as a baseline, the total yield of new spectrum auctions and gains related to 4G technology combined represents 800-1,200 percent of capacity increase. Compared to the outlined demand (the 9,000 percent stated earlier), this indicates a massive 4G capacity gap. To support the expected mobile data traffic volume in 2015, operators will install an order of magnitude more cells during 2013 and 2014 and try out related equipment in 2012 and 2013, which will be developed by mobile equipment vendors in 2011 and 2012.
A shift in the mobile radio access network architecture to the deployment of more and smaller 4G cells is imminent. This will allow the frequent reuse of expensive operator spectrum assets based on newly deployed cell sites and help address the exploding demand for mobile data capacity.
What are compact base stations?
A new base station paradigm designed to enable operators to deploy the necessary cell density in the coming years must be a priority design target for equipment vendors. Compact Base Transceiver Stations (Compact BTS) are a mandatory part of near- to medium-term 4G radio access network deployments, with first-generation equipment being deployed in WiMAX today.
Fundamentally System-on-Chip (SoC)-based, Compact BTS equipment combines all the processing layers of a complete base station in a passively cooled single-box form factor that can be mounted just about anywhere power can be found. Single-box outdoor or indoor Compact BTS equipment comes in a variety of enclosures, antenna form factors, and RF output classes (see Table 1). The key requirement of Compact BTS is to enable operators to use any type of real estate or right of way to deploy more cells strictly on a least-cost base. To achieve this, Compact BTS equipment will eliminate requirements for operators to construct, lease, and maintain air-conditioned shelters or cabinets.
While operators will have to accept the requirement to add new cell sites to traditional radio access network locations, there will always be the need to minimize the resulting cost impact. The CAPEX and OPEX involved in acquiring, building out, installing, and operating additional cell sites will cause operators to minimize and gradually increase the total number of added sites.
To maximize the spectral efficiency and capacity yield of each new cell, Compact BTS equipment employs all the bells and whistles of evolving 4G technology:
- Support of wide spectrum channels for 4G mobile broadband usage
- Up to 40 MHz Frequency Division Duplex (FDD) LTE and 80 MHz Time Division Duplex (TDD) LTE of total channel capacity
- Flexible support of FDD and TDD spectrum usage
- Maximum reuse of available spectrum from any given cell site
- Cost-effective multisector deployment options for all Compact BTS
- Multicarrier spectrum aggregation to create virtual 4G service channels
- Extensive support of 4G Adaptive Antenna System (AAS) technology
- Minimum of 4 Tx and 4 Rx streams, with processing support for MU-MIMO
- Optional support of 8 Tx and 8 Rx antennas, with AAS signal processing support, such as beam forming, interference cancellation, and so on
- Support of Self-Organized Network (SON) software technology
- Initial autodiscovery, self-configuration, and network operations center autoconnect capability
- Automated self-configuration, ongoing maintenance, and RF operation
At the same time, Compact BTS equipment needs to support infrastructure-grade operations requirements and meet requirements related to equipment practice that allow the deployment of carrier-grade, high-density radio access networks:
- Extremely compact, passively cooled, single-box equipment options
- Minimum power consumption, with software-optimized Power Amplifier (PA) efficiency
- Minimum size and weight, enabling single-craft installation
- Long-term deployment viability
- In-field software upgradability: Fully software-defined BTS architecture
- In-field software evolution: Support of future mobile standards evolution
- In-field software backward compatibility: Concurrent support of multiple mobile standards
- In-field RF evolution: Continued reuse of initially deployed spectrum
- Operational infrastructure requirements
- Very high MTBF, at least comparable to acceptable Remote Radio Head (RRH) metrics
- Extensive support of real-time diagnostics, statistics, alarming, and logging
- 100 percent operability from the central network operations center, especially under system error conditions
Compact BTS equipment must be cost-effective, not only in its deployment impact, but also in terms of equipment and ongoing support costs. The bottom line is simple: Once an order of magnitude of additional 4G cell sites is installed, revisiting these cell sites should not be required for a long time.
First-generation single-carrier WiMAX deployments
The aforementioned requirements can only be supported based on a new generation of silicon solutions: multilayer, multicore[
] SoCs. These SoCs offer multiple targeted processing layers for various BTS architecture subsystems – CPU cores for system and service management, RISC cores with hardware acceleration for network layer and data path processing, DSP[] cores with hardware acceleration for PHY layer and AAS processing, and additional DSP cores with hardware acceleration for the software-defined implementation of the Digital RF Front-End (DFE) layer.
With the integration of all base station processing layers, modern SoC-based Compact BTS design eliminates almost all discrete components found in traditional base stations while maintaining high performance. This is the only way to satisfy the extremely stringent requirements for maintaining low size, weight, and power consumption while still supporting medium- and high-power PA options.
Reducing the entire base station design to a single SoC integrated with a suitable RF subsystem, Compact BTS equipment consumes a mere fraction of traditional BTS’s system power and delivers a higher MTBF than even stand-alone RRH equipment, combining flexible RF/PA solutions with complete BTS functionality in one compact, passively cooled box.
The first generation of this Compact BTS equipment is now available based on DesignArt Networks’ DAN2400 SoC, utilizing the ultra-compact system architecture depicted in the reference design captured in Figure 2. Compact Pico and MicroBTS products span 2×2 to 6×6 Tx/Rx AAS configurations, with total system output power ranging from 0.5-12 W.
Operators can reduce the 5-year CAPEX and OPEX associated with traditional BTS applications by about 38-47 percent, asserts Monica Paolini, founder and president of Senza Fili Consulting. They can also gain the additional benefit of flexible site selection to expand their networks, such as the ability to deploy in any location that provides for a standard power source and carries suitable antennas.
Second-generation multicarrier 3G and 4G solutions
The latest edition of multilayer, multicore SoCs takes the Compact BTS design architecture several steps further, first extending the range of Compact BTS applications from 0.25 W indoor access points up to 80 W macrocells, then adding connection options to build ultra-scalable, distributed, multisector Compact BTS and RRH applications. All of these applications are entirely based on passively cooled single-box equipment, thus covering mobile operators’ site specifications without the need for any shelter.
The critical benefit for operators and vendors is that all of these design options use the same baseband, control plane, and backhaul hardware and software subsystems. Thus vendors can use a single R&D framework for an entire product line (back to Table 1), in turn furnishing operators with coherent end-to-end operational, network, and service behavior of densely deployed Compact BTS infrastructure.
Combining a scalable, embedded, multilayer, multicore BTS architecture with a fully software-defined multicarrier, multimode digital radio front end embedded in a single SoC brings additional benefits, including the ability to operate multiple mobile radio access technologies simultaneously from the same Compact BTS (see Figure 3).
Second-generation Compact BTS equipment based on DesignArt Networks’ DAN3000 SoC family supports in-field software upgradability to future 4G mobile access technologies while maintaining backward compatibility with existing 2G or 3G subscribers. As mobile service access technology evolves and subscribers migrate to newer devices, multicarrier Compact BTS equipment can reuse and aggregate initially deployed spectrum assets, combining multiple carriers to form virtual 4G service channels.
Once the carrier-grade, multigigabit radio access network solution based on dense deployment of cost-effective Compact BTS equipment is installed, operators will not need to revisit deployment sites for in-field software upgrades. Utilizing this advanced SoC design approach, vendors can drastically improve margins in highly competitive traditional base station segments while using the same development investment to capture market share in the exploding Compact BTS market.
DesignArt Networks +972 9 7421306 www.designartnetworks.com
