Multi-Standards Radio Base Station (MSR-BS) in 3GPP Release 9

I wrote about Future Mobile Terminals earlier which will probably be Multiservice, Multinetwork and Multimode. A similar approach would be needed for the network side. 3GPP is working on Release-9 feature of Multi-Standard Radio (MSR-BS). The 3GPP Spec 37.900 is not yet available but a draft should be available soon.

Research and Markets have already released a report arguing about the benefits of MSR-BS. Last year Ericsson released the RBS 6000 series products that has MSR support. Huawei and Nokia Siemens Networks are also working on similar products under different guises. Martin has blogged about this topic as well earlier in case you want to refer to.

According to Research and Markets report the terms used for this technology is Multi-Standard Radio Base Station (MSR-BTS/MSR-BS), Multi-Mode Radio Base Station (MMR-BTS/MMR-BS) and Multi-Radio Access Technology (Multi-RAT). The name in standards usually is MSR-BS.

So what is MSR-BS? The 3GPP definition is: Base Station characterized by the ability of its receiver and transmitter to process two or more carriers in common active RF components simultaneously in a declared RF bandwidth, where at least one carrier is of a different RAT than the other carrier(s).

In very simple terms, a single Base Station will be able to simultaneously transmit different radio access technologies from a single unit. So a unit may be for example transmitting GSM, WCDMA 2100 and LTE 2600 simultaneously.

The number of technologies supported by a BTS will be an implementation choice. With technology maturing it wont be surprising to have upto 4-5 different technologies in a MSR-BS in the next five years.

The advantage the mobile operator will have will not only be monetary but there will be possibility of space saving. But as the old english proverb says, they will be "putting their eggs in a single basket". If one unit stops working then the coverage in the area goes down. There may not be an option to fallback on different technology.

The way this MSR-BS are implemented will be definitely based on Software Defined Radios (SDR). The advantage with SDR will be that in different parts there is a slight frequency variation for different technologies like GSM-850 is specific to USA whereas the rest of the world uses GSM-900. These small variations will easily be customisable with these MSR-BS and optimisations wont be too far off.

Different Band Categories have been defined for different scenarios. For example Band Category 1 involves deplyment where GSM wont be present. Only LTE and WCDMA is present there. Band Category 2 involves frequency bands where GSM, EDGE, WCDMA and LTE may be present. Band Category 3 is designed with TDD and TD-SCDMA in mind.

More information as and when available

SDR: Today and Future

I also got an opportunity to attend the SDR briefing in LTE World Summit. There were many interesting presentations including one titled "SDR in Mobile Devices" by Thierry Dubois, SDR Market Analyst, IMEC, Belgium. Infact last year I blogged about SDR from Imec presentation as well. The following is an extract from Thierry's presentation:

The key benefits of SDR are as follows:

• Reducing the Bill Of Materials (BOM)
• Lower development costs
• Facilitate better reuse of intellectual property (IPR)
• Possibility to upgrade products already in the field
• Enabler of the Cognitive Radio vision

There are three main areas where SDR's are required but some problems exist as can be seen from the diagram above.

• Flexibility is the key for baseband. Some of the common signal processing blocks may not be reusable. This means that though some protocols can easily be defined for a particular baseband, others may not be possible for that baseband. Good progress is still being made though on this front.
• Reconfigurable RF is some way away, further down the road.
• The biggest challenge is the antenna interface for which no proper solution exists. Some solutions being worked on right now include MEMS based solution, Carbon nanotubes, Special ceramic materials, etc.

The next step after SDR is cognitive radio (CR). The main advantage for using CR would be because spectrum is over-allocated but under-utilised. There are lots of white spaces in the spectrum that could be utilised by devices intelligently of their own.

Cognitive Radios are defines as: A radio that can autonomously change its parameters based on interaction with, and possibly learning of, the environment in which it operates. Through appropriate radio resource management, such a cognitive radio should make flexible and efficient use of network/spectrum resources.

CR would consist of Intelligent Sensing hardware and Intelligent Sensing Algorithms. There are two types of CR being considered:

• Opportunistic Radio: A radio that co-exists with other systems using the same spectrum. E.g., White Space Devices
• Smart Reconfigurable Radio Systems: A radio that makes flexible and efficient use of network/spectrum resources across heterogeneous environments. Seamlessly roaming possible on different networks, countries, frequencies, etc. It requires true paradigm shift i.e., spectrum liberalization

An Introductory paper on SDR is available on Bitwave Semiconuctor website.

SDR for LTE

Image above shows a Mobile Phone with and without SDR

Since LTE will have highly flexible bandwidth and it would be possible to use phones in many different bands with facility for reprogramming if the operator you are using your phone with has completely different frequency band it is being proposed that Software Defined Radio (SDR) be used with LTE.

I am not aware as of now a practical mobile device with SDR so this would be an interesting leap if adopted by the mobile manufacturers.

Cognitive radio

Cognitive radio (CR) is a newly emerging technology, which has been recently proposed to implement some kind of intelligence to allow a radio terminal to automatically sense, recognize, and make wise use of any available radio frequency spectrum at a given time. The use of the available frequency spectrum is purely on an opportunity driven basis. In other words, it can utilize any idle spectrum sector for the exchange of information and stop using it the instant the primary user of the spectrum sector needs to use it. Thus, cognitive radio is also sometimes called smart radio, frequency agile radio, police radio, or adaptive software radio,1 and so on. For the same reason, the cognitive radio techniques can, in many cases, exempt licensed use of the spectrum that is otherwise not in use or is lightly used; this is done without infringing upon the rights of licensed users or causing harmful interference to licensed operations.

The only difference with SDR (Software Defined Radio) is that a cognitive radio needs to scan a wide range of frequency spectra before deciding which band to use, instead of a predefined one, as an SDR terminal does. One of the most important characteristic features of an SDR terminal is that its signal is processed almost completely in the digital domain, needing very little analogue circuit. This brings a tremendous benefit to make the terminal very flexible (for a multimode terminal) and ultrasmall size with the help of state-of-the-art microelectronics technology.

More Information at:

http://www.technologyreview.com/read_article.aspx?ch=specialsections&sc=emergingtech&id=16471

http://www.ece.gatech.edu/research/labs/bwn/CR/Projectdescription.html

http://en.wikipedia.org/wiki/Cognitive_radio