Radio relay technologies in LTE-Advanced

The following is from NTT Docomo Technical journal: 

Three types of radio relay technologies and their respective advantages and disadvantages are shown in Figure 1. 

A layer 1 relay consists of relay technology called a booster or repeater. This is an Amplifier and Forward (AF) type of relay  technology by which Radio Frequency (RF) signals received on the downlink from the base station are amplified and transmitted to the mobile station. In a similar manner, RF signals received on the uplink from the mobile station are amplified and transmitted to the base station. The equipment functions of a layer 1 relay are relatively simple, which makes for low-cost implementation and short processing delays associated with relaying. With these  features, the layer 1 relay has already found widespread use in 2G and 3G mobile communication systems. It is being deployed with the aim of improving coverage in mountainous regions, sparsely populated areas and urban areas as well as in indoor environments.


The RF performance specifications for repeaters have already been specified in LTE, and deployment of these repeaters for the same purpose is expected. The layer 1 relay, however, amplifies intercell interference and noise together with desired signal components thereby deteriorating the received Signal to Interference plus Noise power Ratio (SINR) and reducing the throughput enhancement gain.


The layer 2 relay, meanwhile, is a Decode and Forward (DF) type of relay technology by which RF signals received on the downlink from the base station are demodulated and decoded and then encoded and modulated again before being sent on to the mobile station. This demodulation and decoding processing performed at the radio relay station overcomes the drawback in layer 1 relays of deteriorated received SINR caused by amplification of intercell interference and noise. A better throughput-enhancement effect can therefore be expected compared with the layer 1 relay. At the same time, the layer 2 relay causes a delay associated with modulation/demodulation and encoding/decoding processing. In this type of relay, moreover, radio functions other than modulation/demodulation and encoding/decoding (such as mobility control, retransmission control by Automatic Repeat request (ARQ), and user-data concatenation/segmentation/reassembly) are performed between the base station and mobile station transparently with respect to the radio relay, which means that new radio-control functions for supporting this relay technology are needed. 

The layer 3 relay also performs demodulation and decoding of RF signals received on the downlink from the base station, but then goes on to perform processing (such as ciphering and user-data concatenation/segmentation/reassembly) for retransmitting user data on a radio interface and finally performs encoding/modulation and transmission to the mobile station. Similar to the layer 2 relay, the layer 3 relay can improve throughput by eliminating inter-cell interference and noise, and additionally, by incorporating the same functions as a base station, it can have small impact on the standard specifications for radio relay technology and on implementation. Its drawback, however, is the delay caused by user-data processing in addition to the delay caused by modulation/demodulation and encoding/decoding processing.


In 3GPP, it has been agreed to standardize specifications for layer 3 relay technology in LTE Rel. 10 because of the above features of improved received SINR due to noise elimination, ease of coordinating standard specifications, and ease of implementing the technology. Standardization of this technology is now moving forward.


Layer 3 radio relay technology is shown in Figure 2. In addition to performing user-data regeneration processing and modulation/demodulation and encoding/ decoding processing as described above, the layer 3 relay station also features a unique Physical Cell ID (PCI) on the physical layer different than that of the base station. In this way, a mobile station can recognize that a cell provided by a relay station differs from a cell provided by a base station.


In addition, as physical layer control signals such as Channel Quality Indicator (CQI) and Hybrid ARQ (HARQ) can terminate at a relay station, a relay station is recognized as a base station from the viewpoint of a mobile station. It is therefore possible for a mobile station having only LTE functions (for example, a mobile station conforming to LTE Rel. 8 specifications) to connect to a relay station. Here, the wireless backhaul link (Un) between the base station and relay station and the radio access link (Uu) between the relay station and mobile station may operate on different frequencies or on the same frequency. In the latter case, if transmit and receive processing are performed simultaneously at the relay station, transmit signals will cause interference with the relay station’s receiver by coupling as long as sufficient isolation is not provided between the transmit and receive circuits. Thus, when operating on the same frequency, the wireless backhaul-link and radio-access-link radio resources should be subjected to Time Division Multiplexing (TDM) so that transmission and reception in the relay station are not performed simultaneously.

Scenarios in which the introduction of relay technology is potentially useful have been discussed in 3GPP. Deployment scenarios are shown in Table 1. Extending the coverage area to mountainous and sparsely populated regions (rural area and wireless backhaul scenarios) is an important scenario to operators. It is expected that relay technology can be used to economically extend coverage to such areas as opposed to deploying fixed-line backhaul links. Relay technology should also be effective for providing temporary coverage when earthquakes or other disasters strike or when major events are being held (emergency or temporary coverage scenario), i.e., for situations in which the deployment of dedicated fixed-line backhaul links is difficult. In addition, while pico base stations and femtocells can be used for urban hot spot, dead spot, and indoor hot spot scenarios, the installation of utility poles, laying of cables inside buildings, etc. can be difficult in some countries and regions, which means that the application of relay technology can also be effective for urban scenarios. Finally, the group mobility scenario in which relay stations are installed on vehicles like trains and buses to reduce the volume of control signals from moving mobile stations is also being proposed.


In 3GPP, it has been agreed to standardize the relay technology deployed for coverage extension in LTE Rel. 10. These specifications will, in particular, support one-hop relay technology in which the position of the relay station is fixed and the radio access link between the base station and mobile station is relayed by one relay station.



References
[1] 3GPP TS36.912 V9.1.0: “Feasibility study for Further Advancement for E-UTRA (LTE-Advanced),” 2010.
[2] 3GPP TS36.323 V9.0.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification,” 2009
[3] 3GPP TS36.322 V9.1.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Link Control (RLC) protocol specification,” 2010.
[4] 3GPP TS36.321 V9.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification,” 2010.
[5] 3GPP TS36.331 V9.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification,” 2010.
[6] 3GPP TS36.413 V9.2.1: “Evolved Universal Terrestrial Radio Access (E-UTRA); S1 Application Protocol (S1AP),” 2010.
[7] 3GPP TR36.806 V9.0.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Relay architectures for E-UTRA (LTEAdvanced),” 2010.
[8] IETF RFC4960: “Stream Control Transmission Protocol,” 2007.
[9] 3GPP TS29.281 V9.2.0: “General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U),” 2010.

Security issues in new technologies

I have attended a lot of events/talks in the last month where people talked about Augmented Reality, Proximity Marketing, QR codes, etc. but nobody seems to talk about security. Its being taken for granted. For example MAC's have been said to be Virus proof and they probably are but other Apps may be infectable and in this case its the Java that has allowed a MAC botnet about 0.6 Million strong.

Some years back proximity marketing via Bluetooth was a big thing and we were lucky to be involved with couple of projects making it possible but then the Bluetooth virus came to light and people stopped leaving their Bluetooth on in public places. Doesnt look like Bluetooth based proximity marketing has gone very far since those days.

QR codes is a simple way to for advertisers redirect the end users to their websites but then recently I read that a rogue QR code can be used to redirect the end users to a site that can be used to hack their phones. The main thing pointed out is that 99% of the time QR codes are read by mobile phones and 99% of these phones are either iPhones or Android's, which can help narrow down the exploits.

There is a good chance that when there is mass adoption of these new technologies, Security is going to be a big issue. Not sure if enough is being done. If there are any pointers on security issues please feel free to comment.

Project Glass: One day... By Google

I seem to like the Corning ones more that I blogged here.

** New Edits 05/04/12 09:40 **
From CNET:

Google's augmented reality glasses are real! Dubbed Project Glass, the long-rumoured lenses that show you heads-up information about the world around you have been confirmed by the company.

At the moment, Google's announcement is limited to a Google+ page

Here is a parody on above video from Tom Scott:

What is nano-SIM card

BBC reported that there is some dispute between Apple and Nokia/Rim for the next generation of SIM cards, 'nano-SIM'. You can read more about that here.

While looking for how the nano-SIM is different from other SIM cards I came across an interesting presentation from G&D. The above picture summarises the different types of SIM cards in use. The following is an extract from their whitepaper:


When the GSM network first appeared, mobile devices resembled bricks or even briefcases, and SIM cards were the size of credit cards. The subsequent miniaturization of the phones led to the standardization of smaller SIMs, the Plug-in SIM, and later the Mini-UICC also known as 3rd form factor (3FF). With the introduction of Apple’s iPad, the 3FF, or the Micro-SIM as it was then called, established itself widely in the market.

Nevertheless, the trend towards miniaturization of the SIM card is still not over. The latest form factor which is currently in discussion at ETSI (European Telecommunications Standards Institute) is the 4th form factor (4FF) or Nano-SIM. Measuring 12.3 x 8.8 mm, the Nano-SIM is about 30 percent smaller than the Micro-SIM. Even the thickness (0.7 mm) of the card has been reduced by about 15 percent – a tremendous technical challenge.

The Nano-SIM offers device manufacturers the crucial advantage of freeing up extra space for other mobile phone Nano-SIM The smallest SIM form factor on the market components such as additional memory or larger batteries. Popular smart phones in particular have to strike a balance between the need for components that are more powerful but bulkier and a slim design. The reduced volume of the 4FF gives manufacturers the opportunity to produce devices that are thinner and more appealing.


In case you were wandering the differences that are causing the disagreements, here are the differences between the formats:

Joyn = SMS v2.0?

'Joyn' is the brand name for the RCS services that have been around in the name for a long while. Yesterday someone sent this link for the Fierce Wireless article that had the link to the above Vodafone video.

In theory this sounds great but in practice it may be a bit difficult for operators to sell. One of the selling point for this service is that it is going to be part of the standards so independent of the platform. Android and iOS are the two most popular platforms and more and more users are adopting them. The OTT apps are now available on both these platforms, meaning that it will have mass market adoption. If some other platforms have to succeed then they have to make these most popular apps available on their platform or they will not survive. Microsoft has been rumoured to have paid Rovio to develop the first Angry Birds for the WP platform and they may have to do the same again since the new Angry Birds space is not available on the Windows mobile platform.

In any case, Joyn may be good and it can provide enhanced services but I have a feeling that it may be a bit too little and too late to succeed.

IMS Release 10 Tutorial

IMS Release 10 Tutorial

View more documents from Zahid Ghadialy

Available to download from here.

Network sharing and other means to leapfrog operator efficiencies

Ultra-efficient network factory: Network sharing and other means to leapfrog operator efficiencies.

View more presentations from Kim Kyllesbech Larsen

DOCOMO Euro-Labs: LTE/LTE-A Interference Coordination for Femtocells

LTE/LTE‐A Interference Coordination for Femtocells

View more presentations from Zahid Ghadialy

A video of this above presentation is embedded below:

Available to download from here.

Platinum Band: Sub 1GHz Frequency Band

Was listening to the Softbank webcast earlier about why they are so happy on receiving the 900MHz spectrum. The extract from slidepack summarises the advantages on this 'Platinum Band'

LTE/LTE-A SON (for Femtocells)

LTE/LTE-A SON (for Femtocells)

View more presentations from Zahid Ghadialy

A Video presentation of the above is embedded below:



PDF of the above presentation is available here.