Tuesday, 23 February 2010

Codec's for LTE

Sometime back I mentioned about Orange launching AMR-WB codec which would result in 'hi-fi quality' voice (even though its being referred to as HD voice by some). Since then, there has been not much progress on this HD-voice issue. CODEC stands for “COder-DECoder,” but is also known as an enCOder-DECoder and COmpression-DECompression system when used in video systems. Codec's are important as they compress the voice/video data/packets so less bandwidth is required for the data to be transmitted. At the same time it has to be borne in mind that the capacity to withstand errors decrease with higher compression ratio and as a result it may be necessary to change the codecs during the voice/video call. This calls for flexibility as in case of AMR (Adaptive Multi Rate) Codecs. The following is from Martin Sauter's book "Beyond 3G – Bringing Networks, Terminals and the Web Together": Voice codecs on higher layers have been designed to cope with packet loss to a certain extent since there is not usually time to wait for a repetition of the data. This is why data from circuit-switched connections is not repeated when it is not received correctly but simply ignored. For IP sessions, doing the same is difficult, since a single session usually carries both real-time services such as voice calls and best-effort services such as Web browsing simultaneously. In UMTS evolution networks, mechanisms such as ‘Secondary PDP contexts’ can be used to separate the real-time data traffic from background or signaling traffic into different streams on the air interface while keeping a single IP address on the mobile device. UMTS uses the same codecs as GSM. On the air interface users are separated by spreading codes and the resulting data rate is 30–60 kbit/s depending on the spreading factor. Unlike GSM, where timeslots are used for voice calls, voice capacity in UMTS depends less on the raw data rate but more on the amount of transmit power required for each voice call. Users close to the base station require less transmission power in downlink compared with more distant users. To calculate the number of voice calls per UMTS base station, an assumption has to be made about the distribution of users in the area covered by a cell and their reception conditions. In practice, a UMTS base station can carry 60–80 voice calls per sector. A typical three-sector UMTS base station can thus carry around 240 voice calls. As in the GSM example, a UMTS cell also carries data traffic, which reduces the number of simultaneous voice calls. The following is an extract from 3G Americas white paper, "3GPP Mobile Broadband Innovation Path to 4G: Release 9, Release 10 and Beyond: HSPA+, SAE/LTE and LTE-Advanced,": Real-time flows (voice/video) based on rate adaptive codecs can dynamically switch between different codec rates. Codec rate adaptation allows an operator to trade off voice/video quality on one side and network capacity (e.g. in terms of the number of accepted VoIP calls), and/or radio coverage on the other side. Operators have requested a standardized solution to control the codec rate adaptation for VoIP over LTE, and a solution has been agreed upon and specified in the 3GPP Rel-9 specifications, which is provided in this paper. CODEC RATE ADAPTATION BASED ON ECN Given previous discussion in 3GPP (3GPP S4-070314) it was clear that dropping IP packets was not an acceptable means for the network to trigger a codec rate reduction. Instead an explicit feedback mechanism had to be agreed on by which the network (e.g. the eNodeB) could trigger a codec rate reduction. The mechanism agreed on for 3GPP Rel-9 is the IP-based Explicit Congestion Notification (ECN) specified in an IETF RFC. ECN is a 2 bit field in the end-to-end IP header. It is used as a “congestion pre-warning scheme” by which the network can warn the end points of incipient congestion so that the sending endpoint can decrease its sending rate before the network is forced to drop packets or excessive delay of media occurs. Any ECN-based scheme requires two parts: network behavior and endpoint behavior. The first part had already been fully specified in an IETF RFC106 and merely had to be adopted into the corresponding specifications (3GPP TS 23.401 and 3GPP TS 36.300). The network behavior is completely service and codec agnostic. That is, it works for both IMS and non-IMS based services and for any voice/video codec with rate-adaptation capabilities. The main work in 3GPP focused on the second part: the endpoint behavior. For 3GPP Rel-9, the endpoint behavior has been specified for the Multimedia Telephony Service for IMS (MTSI - 3GPP TS 26.114). It is based on a generic (i.e. non-service specific) behavior for RTP/UDP based endpoints, which is being standardized in the IETF. Furthermore, it was agreed that no explicit feedback was needed from the network to trigger a codec rate increase. Instead, the Rel-9 solution is based on probing from the endpoints – more precisely the Initial Codec Mode (ICM) scheme that had already been specified in 3GPP Rel-7 (3GPP S4-070314). After the SIP session has been established, the sending side always starts out with a low codec rate. After an initial measurement period and RTCP receiver reports indicating a “good channel,” the sending side will attempt to increase the codec rate. The same procedure is executed after a codec rate reduction. Figure 6.8 depicts how codec rate reduction works in Rel-9:
  • Step 0. The SIP session is negotiated with the full set of codec rates and independent of network level congestion. The use of ECN has to be negotiated separately for each media stream (e.g. VoIP).
  • Steps 1 and 2. After ECN has been successfully negotiated for a media stream the sender must mark each IP packet as ECN-Capable Transport (ECT). Two different values, 10 and 01, have been defined in an IETF RFC106 to indicate ECT. However, for MTSI only 10 shall be used.
  • Step 3. To free up capacity and allow more VoIP calls and/or to improve VoIP coverage, the eNodeB sets the ECN field to Congestion Experienced (CE) in an IP packet that belongs to an IP flow marked as ECT. Note that the ECN-CE codepoint in an IP packet indicates congestion in the direction in which the IP packets are being sent.
  • Steps 4 and 5. In response to an ECN-CE the receiving MTSI client issues an RTCP message to trigger a codec rate reduction.
Note that ECN operates in both directions (uplink and downlink) entirely independent and without any interactions. It is very well possible to trigger codec rate adaptation in one direction without triggering it in the other direction. ONGOING WORK IN 3GPP A new work item called, Enabling Encoder Selection and Rate Adaptation for UTRAN and E-UTRAN, has been created for 3GPP Rel-10. Part of this work item is to extend the scope of the codec rate adaptation solution agreed in Rel-9 to also apply to HSPA and non-voice RTP-based media streams. Further Reading:

Monday, 22 February 2010

Femtocells update from Mobile World Congress 2010

Among a host of announcements, the leading silicon supplier for this segment, picoChip, was working hard to maintain its headstart as Qualcomm and others gear up to enter the market. It announced no fewer than six new customers, many coming from the Taiwanese ecosystem that is so vital to the mass adoption and price competitiveness of any emerging consumer product.

The new customers are Alpha Networks, Argela, Askey, C&S Micro, Contela and Zyxel, all of which will use the UK firm's PC302 picoXcell system-on-chip for HSPA(+). This is designed to reduce cost and time to market for vendors, and now has over 20 adopters, including Vodafone's femto supplier Alcatel-Lucent, and AT&T's, Cisco/ip.access.

Meanwhile, the femto players are looking ahead to LTE, where there are many indications from operators that tiny cells will play a big part in the strategy. The devices will be used from day one by some carriers - to offload data from the macrocell or to provide indoor coverage in high frequencies like 2.6GHz. They could also add capacity to deployments in low frequencies like 700MHz and even be used as a starting point for greenfield providers, which could then add macro networks later, explained Simon Saunders, chair of the Femto Forum.

Continuous Computing has been eyeing the femto market for several years from its heartlands in protocol stacks, core networking and traffic shaping. At MWC, it worked with picoChip and Cavium Networks to show the first complete LTE femtocell reference design. Available immediately, this includes the LTE modem, RF and packet processors, protocol software, intelligent router functionality and a complete Evolved Packet Core (EPC) simulator.

"The demand for LTE femtocells is unquestionable. We are already seeing operators asking for small cell access points to start testing in the second half of this year. Femtocells represent the key to avoiding the difficulties surrounding the first 3G deployments where roll-outs cost too much, took too long and did not meet user expectations," said Mike Dagenais, CEO of Continuous.

The reference design used a picoChip modem, mezzanine RF card and PHY software; Cavium's Octeon Plus multicore processor; and Continuous' Trillium LTE Layer 2/3 protocols, eNodeB reference application and EPC emulator.

Call it network congestion, capacity crunch or data overload - the complaints aired at the Mobile World Congress in Barcelona this week were all about cellphone network operators trying to find ways of profitably handling an explosion in mobile data traffic.

Management of the data traffic has become a priority for the telecoms industry as mobile internet usage is booming but data revenues for the phone companies grow slowly at best.

Research firm Informa forecasts a 50 per cent rise in mobile data traffic in 2010 on the back of the increasing popularity of devices such as the Apple iPhone and netbooks, but only a 13 percent rise in data revenues.

This has put added pressure on the phone companies to find ways of using fixed line networks including the internet to take some of the strain off the airwaves.

"Offloading is crucial for us," France Telecom -owned Orange's global head of mobile Olaf Swantee told Reuters ahead of the conference.

"In many countries where we have a fixed network we try to offload directly," he said.

The problem is that offloading data from wireless network to local hotspots still costs money, and operators are searching left and right for solutions that will not raise their overall capital spending, industry executives said.

"To address the smartphone challenge they are investing again," said Rajeev Suri, chief executive of joint venture equipment maker Nokia Siemens, who added that it was uncertain whether this spending was additional to or instead of other investment plans.

More certain was Bruce Brda, head of rival Motorola's networks business. "Carriers have been very consistent - they do not increase capex," he told Reuters.

Nevertheless Motorola saw better than expected demand late last year for equipment as some operators strengthened their existing networks to cope with surging data traffic, Brda said.

"In early 2010 I am seeing the same trend. The indication is there is incremental spending."

Equipment vendors such as Ericsson, Nokia Siemens and Alcatel-Lucent were also demonstrating new technology LTE equipment in Barcelona, as a route toward handling the data rush.

Operators are expected to spend billions of euros converting their networks to the Long Term Evolution standard, which will enable fast mobile broadband access for services such as watching movies on mobile phones, although some critics say LTE would prove a stopgap solution if data traffic goes on growing.

"LTE will buy a carrier two to three years of relief, but then it runs out," Brda said.

And analysts say telecom operators' sales in mature markets are not growing fast enough to justify major investments, which may mean an increase in demand instead for other technologies such as Wi-Fi or femtocells.

Femtocells are localized phone network base stations sited in homes and offices where signal strength might otherwise be weak, taking users onto the phone company's network via their own broadband internet connections.

"The biggest problem is that everybody is expecting these huge amounts of data but nobody is willing to pay much extra for it," said Stephen Rayment, chief technology officer of Belair Networks, which provides Wi-Fi services.

"Operators started offering 'all you can eat' data and now that's coming back to bite them," he said.

Speaking at Mobile World Congress Professor Simon Saunders, chairman of the femtoforum - the official non-profit standards' body proclaimed "2010 is the breakthrough year for femtocell".

From a UK perspective he was able to confirm the backing of industry regular Ofcom while T-Mobile, Telefonica/O2, Vodafone and Orange have all signed up as members so far. Furthermore, deployment of femtocell solutions to compete with Sure Signal is now ready and in their hands.

"The technology is there and it is now a matter of timing for the operators," he told me. "I cannot give specific dates, but all UK operators should be looking at a 2010 roll-out."

So far 55 network operators are femtocell forum members around the world, and operator commitments have jumped 50 per in the last three months alone. On top of this 3GPP has formalised femtocell standards, and the body's next generation ('Release 9') will bring support for LTE and enhancements for UMTS. The WiMax Forum is also on board as is the FCC in the US while China and Japan have confirmed their support.

Alcatel-Lucent recently announced the availability of a “small cell” (femtocell) designed to address the needs of enterprise customers. And last month Vodafone renamed its femtocell device to Sure Signal, as well as dramatically reducing its cost from £160 down to £50.

Informa said that the Vodafone relaunch of its femtocell offering is “realising considerable success in the UK, spearheading the entrance of femtocell services in the European market.”

“Vodafone rebranded the femtocell service to make the proposition clearer to end users while differentiating from their competition by eliminating indoor coverage deadspots,” it added.

According to Informa there are currently 12 service commitments, including nine commercial launches and several ongoing trials, while completed trials are now progressing into deployment plans for several mobile operators. This contrasts with eight femtocell service commitments and six commercial launches in November 2009.

During the last three months it cited French mobile operator SFR, Portuguese operator OPTIMUS and Chinese operator China Unicom, all of which have commercially launched femtocell services. Meanwhile it says that both Japan’s KDDI and France’s free have also committed to the technology.

Pictures Source: Trusted Reviews

Thursday, 18 February 2010

LTE Conformance Testing Logs

I have added some LTE Conformance Testing Logs and Description on the 3G4G website at http://www.3g4g.co.uk/Lte/ConformanceTests/

Most of these initial tests have been submitted by Anite who has passed it using the LG dongle above.

Tuesday, 16 February 2010

Self Organizing Networks and Enhancements

I have blogged about SON earlier here and here. The following is an update from the 3G Americas Whitepaper on Mobile Broadband:

SON concepts are included in the LTE (E-UTRAN) standards starting from the first release of the technology (Rel-8) and expand in scope with subsequent releases. A key goal of 3GPP standardization is the support of SON features in multi-vendor network environments. 3GPP has defined a set of LTE SON use cases and associated SON functions. The standardized SON features effectively track the expected LTE network evolution stages as a function of time. With the first commercial networks expected to launch in 2010, the initial focus of Rel-8 has been functionality associated with initial equipment installation and integration.

The scope of the first release of SON (Rel-8) includes the following 3GPP functions, covering different aspects of the eNodeB self-configuration use case:
• Automatic Inventory
• Automatic Software Download
• Automatic Neighbor Relations
• Automatic PCI Assignment

The next release of SON, as standardized in Rel-9, will provide SON functionality addressing more maturing networks. It includes the following additional use cases:
• Coverage & Capacity Optimization
• Mobility optimization
• RACH optimization
• Load balancing optimization

Other SON-related aspects that are being discussed in the framework of Rel-9 include improvement on the telecom management system to increase energy savings, a new OAM interface to control home eNodeBs, UE reporting functionality to minimize the amount of drive tests, studies on self testing and self-healing functions and minimization of drive testing. It should be clarified that SON-related functionality will continue to expand through the subsequent releases of the LTE standard.

The SON specifications have been built over the existing 3GPP network management architecture, reusing much functionality that existed prior to Rel-8. These management interfaces are being defined in a generic manner to leave room for innovation on different vendor implementations. More information on the SON capabilities in 3GPP can be found in 3G Americas’ December 2009 white paper, The Benefits of SON in LTE.

SON technologies have been introduced in Rel-8/Rel-9 to help decrease the CAPEX and OPEX of the system. LTE-Advanced further enhances the SON with the following features:
  • Coverage and Capacity Optimization. Coverage and Capacity Optimization techniques are currently under study in 3GPP and will provide continuous coverage and optimal capacity of the network. The performance of the network can be obtained via key measurement data and adjustments can then be made to improve the network performance. For instance, call drop rates will give an initial indication of the areas within the network that have insufficient coverage and traffic counters can be used to identify capacity problems. Based on these measurements, the network can optimize the performance by trading off capacity and coverage.
  • Mobility Robustness Optimization. Mobility Robustness Optimization aims at reducing the number of hand over related radio link failures by optimally setting the hand over parameters. A secondary objective is to avoid the ping-pong effect or prolonged connection to a non-optimal cell.
  • Mobility Load Balancing. Related to Mobility Robustness is Mobility Load Balancing, which aims to optimize the cell reselection and handover parameters to deal with unequal traffic loads. The goal of the study is to achieve this while minimizing the number of handovers and redirections needed to achieve the load balancing.
  • RACH Optimization. To improve the access to the system, RACH Optimization has been proposed to optimize the system parameters based upon monitoring the network conditions, such as RACH load and the uplink interference. The goal is to minimize the access delays for all the UEs in the system and the RACH load.

In addition to the enhanced SON technologies described above, minimization of manual drive testing functionality is also currently under examination in 3GPP to enhance and minimize the effort for optimization of the LTE-Advance network. The main goal is to automate the collection of UE measurement data. In so doing, it will minimize the need for operators to rely on manual drive tests to optimize the network. In general, a UE that is experiencing issues, such as lack of coverage, traffic that is unevenly distributed or low user throughput, will automatically feed back measurement data to the network which may be used by the network as a foundation for network optimization.

SON related 3GPP references can be found on Martin Sauter's blog here.

Monday, 15 February 2010

New Technologies for Mobile Phone Theft prevention

Design Out Crime: Mobile Phone solutions from Design Council on Vimeo.

Three prototype solutions for preventing mobile phone theft have been unveiled.

The i-migo, the 'tie' solution and TouchSafe have been developed to counter crimes such as mobile phone identity fraud, which rose by over 70 per cent in 2009.

TouchSafe uses Near Field Communications (NFC) technology similar to that used by the Oyster Card and requires the handset's owner to carry a small card with them that they touch on the phone every time they make a purchase.

The 'tie' solution makes an association between a handset and theSIM chip so that other SIMs cannot be used on the handset should the mobile phone be stolen.

And the i-migo is a small device carried by the mobile phone's owner that sounds an alert and locks the handset should it be taken outside of a set range. Additionally, it automates the back-up of any data stored on the device.

The prototypes were inspired by a Home Office initiative to develop new ways of preventing mobile phone theft and will be shown off atMobile World Congress in Barcelona next week.

Home Office Minister Alan Campbell said: "As new technology creates new opportunities for the user it can also provide criminals with opportunities as well.

"I believe the solutions developed by this challenge have the potential to be as successful as previous innovations like Chip and Pin, which reduced fraud on lost or stolen cards to an all-time low, and would encourage industry to continue working with us and take them up," Campbell continued.

Sunday, 14 February 2010

LTE World Summit promising to be a grand event

The LTE World Summit which is in its 6th year is promising to be a much bigger event with more than 150 speakers and 80 exhibitors. There is also the first LTE Awards program which is something to look forward to.

A quick glance at the program shows that there will be a very interesting mix of people including operators, handset vendors, chipset manufacturers, analysts and ofcourse bloggers like myself. There will be so many things to cover that three days probably may not be enough and it will take couple of weeks to go through all the information and digest it.

You can have a look at the old and the latest brochure at http://www.3g4g.co.uk/Temp/