Tuesday, 30 November 2010

Presentation: Further Enhancements for LTE-Advanced

Monday, 29 November 2010

LSTI: Job nearly done!

According to Mobile Europe magazine, LSTI has nearly completed the tasks it had been created for. The following is from the report:

LSTI said it has reached Milestones for Interoperability Development Tests (IODT), Interoperability Tests (IOT) and for Friendly Customer Trials (FCT). With these Milestones complete, LSTI said it could move to its last working phase and "finish all LTE trials in a timely manner".

Following on from the Proof of Concept (PoC) tests, which was the first testing phase of the LSTI alliance, and which was completed a year ago, LSTI has now completed all Interoperability Development Tests (IODT) for both FDD (Frequency Division Duplex) and TDD (Time-Division Duplex). Furthermore, penultimate Milestone for Interoperability Tests (IOT) has also been passed. That means that the LSTI members have proved that at least three vendors for each case are about to deliver to the market interoperability tested access network and terminal equipment.

The Core Network Interface S1 (Connection Access Network to Core) IOT is almost completed and more results are expected to be delivered soon.

“Overall these results are well aligned with the previous results shared in the LSTI PoC phase. This testing and the co-operation of the vendors and operators involved have brought forward the growth of the LTE ecosystem and enabled a accelerated commercialisation of LTE-EPC by fostering technology alignment across all parties”, said Christian Kuhlins, LSTI Activity Manager IOT, Ericsson AB. “We can now see that the telecommunications industry is about to launch LTE/SAE equipment. More and more commercial network and terminal equipment will be available on the market very soon.”

Eleven LSTI operators have set-up their LTE/EPC trials and have already delivered reports built on a common testing methodology. The Trial Group has achieved one major step in passing the “Radio Access Testing” milestone which includes: Latency, State Transition, Throughput, Cell Capacity, Mobility, Basic Quality of Service and User Experience testing domains.

LSTI said that last results are expected during the next few weeks and will be presented at the Mobile World Congress 2011.

Friday, 26 November 2010

Iridium NEXT: Next Generation Satellite Network

Presented by Dan Mercer, VP & General Manager, EMEA & Russia on November 9th , 2010 at Digital Communications Knowledge Transfer Network And Cambridge Wireless Future Wide Area Wireless SIG – ‘Networks and the New Economy’

To download see: http://www.cambridgewireless.co.uk

Thursday, 25 November 2010

LIPA, SIPTO and IFOM Comparison

Enhancing macro radio access network capacity by offloading mobile video traffic will be essential for mobile communications industry to reduce its units costs to match its customer expectations. Two primary paths to achieve this are the use of femtocells and WiFi offloading. Deployment of large scale femtocells for coverage enhancement has been a limited success so far. Using them for capacity enhancements is a new proposition for mobile operators. They need to assess the necessity of using them as well as decide how to deploy them selectively for their heavy users.

Three alternative architectures that are being standardized by 3GPP have various advantages and shortcomings. They are quite distinct in terms of their dependencies and feasibility. Following table is a summary of comparison among these three approaches for traffic offloading.

Looking at the relative strengths of the existing traffic offload proposals, it is difficult to pick an outright winner. SIPTO macro-network option is the most straight-forward and most likely to be implemented rather quickly. However, it doesn't solve the fundamental capacity crunch in the radio access network. Therefore its value is limited to being an optimization of the packet core/transport network. Some other tangible benefits would be reduction in latency to increase effective throughput for customers as well as easier capacity planning since transport facilities don't need to be dimensioned for large number of radio access network elements anymore.

LIPA provides a limited benefit of allowing access to local premises networks without having to traverse through the mobile operator core. Considering it is dependent on the implementation of femtocell, this benefit looks rather small and has no impact on the macro radio network capacity. If LIPA is extended to access to Internet and Intranet, then the additional offload benefit would be on the mobile operator core network similar to the SIPTO macro-network proposal. Femtocell solves the macro radio network capacity crunch. However, the pace of femtocell deployments so far doesn't show a significant momentum. LIPA's market success will be limited until cost of femtocell ownership issues are resolved and mobile operators decide why (coverage or capacity) to deploy femtocells.

IFOM is based upon a newer generation of Mobile IP that has been around as a mobile VPN technology for more than 10 years. Unfortunately success record of mobile IP so far has been limited to enterprise applications. It hasn't become a true consumer-grade technology. Introduction of LTE may change this since many operators spearheading LTE deployments are planning to use IPv6 in handsets and adopt a dual-stack approach of having both IPv4 and IPv6 capability. Since many WiFi access networks will stay as IPv4, DSMIPv6 will be the best tunneling mechanism to hide IPv6 from the access network. Having dual-stack capability will allow native access to both legacy IPv4 content and native IPv6 content from major companies such as Google, Facebook, Yahoo, etc. without the hindrance of Network Address Translation (NAT). Considering the popularity of smartphones such as iPhone, Blackberry and various Android phones, they will be the proving ground for the feasibility of DSMIPv6.

Source of the above content: Whitepaper - Analysis of Traffic Offload : WiFi to Rescue

Wednesday, 24 November 2010

IP Flow Mobility and Seamless Offload (IFOM)

Unlike LIPA or SIPTO that are dependent on upstream network nodes to provide the optimization of routing different types of traffic, IFOM relies on the handset to achieve this functionality. It explicitly calls for the use of simultaneous connections to both macro network, e.g., LTE, UMTS and WiFi. Therefore, IFOM, unlike LIPA and SIPTO, is truly a release 10-onward only technology and it is not applicable for user terminals pre-Release 10. IFOM is being specified via 3GPP TS 23.261 [1]. Following diagram shows the interconnectivity model for IFOM capable UE.

IFOM uses an Internet Engineering Task Force (IETF) Request For Comments (RFC), Dual Stack Mobile IPv6 (DSMIPv6) (RFC-5555) [2].

Since IFOM is based on DSMIPv6, it is independent of the macro network flavor. It can be used for a green-field LTE deployment as well as a legacy GPRS packet core.

Earlier on we looked at the mobile network industry attempts of integration between packet core and WLAN networks. Common characteristic of those efforts was the limitation of the UE, its ability to use one radio interface at a time. Therefore, in earlier interworking scenarios UE was forced to use/select one radio network and make a selection to move to an alternative radio for all its traffic. Today many smartphones, data cards with connection managers already have this capability, i.e., when the UE detects the presence of an alternative access network such as a home WiFi AP, it terminates the radio bearers on the macro network and initiates a WiFi connection. Since WiFi access network and packet core integration is not commonly implemented, user typically loses her active data session and re-establishes another one.

Similarly access to some operator provided services may not be achieved over WiFi. Considering this limitation both iPhone IOS and Android enabled smartphones to have simultaneous radio access but limited this functionality to sending MMS over the macro network while being connected to WiFi only.

IFOM provides simultaneous attachment to two alternate access networks. This allows fine granularity of IP Flow mobility between access networks. Using IFOM, it will be possible to select particular flows per UE and bind them to one of two different tunnels between the UE and the DSMIPv6 Home Agent (HA) that can be implemented within a P-GW or GGSN. DSMIPv6 requires a dual-stack (IPv4 or IPv6) capable UE. It is independent of the access network that can be IPv4 or IPv6.

[1] 3GPP TS 23.261: IP flow mobility and seamless Wireless Local Area Network (WLAN) offload; Stage 2

[2] RFC-5555: Mobile IPv6 Support for Dual Stack Hosts and Routers

[3] 3GPP TS 23.327: Mobility between 3GPP-Wireless Local Area Network (WLAN) interworking and 3GPP systems

Content Source: Analysis of Traffic Offload : WiFi to Rescue

Monday, 22 November 2010

Carrier aggregation deployment scenarios for Release-10 LTE-A

One of the important aspects to consider is that carrier aggregation should allow aggregation of not only the existing bands, but also bands that are introduced in future, e.g., 3.5 GHz band, etc. While existing bands already have certain deployments, new deployments can be considered for new bands that are introduced. Since introduction of new bands is done in a release independent fashion, considerations for such future bands are essential already in Rel-10. When higher frequencies such as 3.5 GHz are considered, path loss can be significant (e.g., 4-10 dB difference in link budget) when compared to 2 GHz. Hence, the most efficient deployment may not be to stick with the traditional macro-overlaying approach. Carrier aggregation should allow more flexible use of such new bands, since coverage and mobility can be ascertained by the existing band deployments, e.g., 2 GHz.

Picture below shows some of the potential deployment scenarios for carrier aggregation. Note that the scenarios listed are non-exhaustive. For example, other scenarios using repeaters and femto cells may be considered. Also note that F2 > F1.

Scenario 1
* F1 and F2 cells are co-located and overlaid, providing nearly the same coverage
* Both layers provide sufficient coverage and mobility can be supported on both layers.
* Likely scenario when F1 and F2 are of the same band, e.g., 2 GHz, 800 MHz, etc.
* It is expected that aggregation is possible between overlaid F1 and F2 cells.

Scenario 2
* F1 and F2 cells are co-located and overlaid, but F2 has smaller coverage due to larger path loss
* Only F1 provides sufficient coverage and F2 is used to provide throughput. Mobility is performed based on F1 coverage.
* Likely scenario when F1 and F2 are of different bands, e.g., F1 = {800 MHz, 2 GHz} and F2 = {3.5 GHz}, etc.
* It is expected that aggregation is possible between overlaid F1 and F2 cells.

Scenario 3
* F1 and F2 cells are co-located but F2 antennas are directed to the cell boundaries of F1 so that cell edge throughput is increased
* F1 provides sufficient coverage but F2 potentially has holes, e.g., due to larger path loss. Mobility is based on F1 coverage.
* Likely scenario when F1 and F2 are of different bands, e.g., F1 = {800 MHz, 2 GHz} and F2 = {3.5 GHz}, etc.
* It is expected that F1 and F2 cells of the same eNB can be aggregated where coverage overlap.

Scenario 4
* F1 provides macro coverage and on F2 Remote Radio Heads (RRHs) are used to provide throughput at hot spots
* Mobility is performed based on F1 coverage.
* Likely scenario when F1 and F2 are of different bands, e.g., F1 = {800 MHz, 2 GHz} and F2 = {3.5 GHz}, etc.
* It is expected that F2 RRE cells can be aggregated with the underlying F1 macro cells.

Scenario 5
* Similar to scenario #2, but frequency selective repeaters are deployed so that coverage is extended for one of the carrier frequencies

Scenarios supported in Rel-10 time frame
* For DL, all scenarios are supported in Rel-10
* For UL, scenario 4 and 5 are not supported in Rel-10

Source: R2-100531 CA deployment scenario NTT DOCOMO

Friday, 19 November 2010

CA (Carrier Aggregation) Scenarios in LTE-Advanced

CA (Carrier Aggregation) may be used in three different spectrum scenarios as follows.

Intraband Contiguous CA — This is where a contiguous bandwidth wider than 20 MHz is used for CA. Although this may be a less likely scenario given frequency allocations today, it can be common when new spectrum bands like 3.5 GHz are allocated in the future in various parts of the world. The spacing between center frequencies of contiguously aggregated CCs (Component Carriers) is a multiple of 300 kHz to be compatible with the 100 kHz frequency raster of Release 8/9 and preserving orthogonality of the subcarriers with 15 kHz spacing.

Intraband Non-Contiguous CA — This is where multiple CCs belonging to the same band are used in a non-contiguous manner. This scenario can be expected in countries where spectrum allocation is non-contiguous within a single band, when the middle carriers are loaded with other users, or when network sharing is considered.

Interband Non-Contiguous CA — This is where multiple CCs belonging to different bands (e.g., 2 GHz and 800 MHz are aggregated). With this type of aggregation, mobility robustness can potentially be improved by exploiting different radio propagation characteristics of different bands. This form of CA may also require additional complexity in the radio frequency (RF) front-end of UE. In LTE Release 10, for the UL the focus is on intraband CA, due to difficulties in defining RF requirements for simultaneous transmission on multiple CCs with large frequency separation, considering realistic device linearity. For the DL, however, both intra and interband cases are considered in Release 10, while specific RF requirements are being developed.

Text Source: Carrier Aggregation Framework in 3GPP LTE-Advanced - Mikio Iwamura et al. in IEEE Communications Magazine August 2010

Picture Source: http://www.catr.cn/tecm/dxwjs/201006/t20100610_1143968.htm