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

Presentation: Smart Antennas and SON

Smart Antennas and SON

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Presented by Kevin Linehan, VP, CTO Antennas, Andrew Solutions in the 4G World, Oct. 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

Carrier Aggregation Concepts for LTE Rel-10

Carrier Aggregation Concepts for LTE Rel-10

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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

Quick Recap of Self-Organising Networks (SON)

Aspects of Central SON

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The Path to 4G: LTE and LTE-Advanced

The Path to 4G: LTE and LTE-Advanced

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The Path to 4G: LTE and LTE-Advanced presented by James Seymour, Alcatel Lucent in 4G World, 20th Oct. 2010.

HTML5 for Mobile Devices

I had been recently talking to some developers about the programming and App development on mobiles and quite a few people are of the opinion that HTML5 may help the mobile Apps go to the next level.

The biggest problem HTML5 is supposed to solve is write once run anywhere applicatons. Most of the programs will have the same look and feel if they are run on a PC or mobile and between different devices.

Ofcourse not everything is perfect. There are yet many API's that need to be implemented in for HTML5 like the 3D and Mic API's, etc. Another problem is that a lot of phones are not yet supporting HTML5 and some of them that are supporting, not supporting it completely. This will have to be solved asap.

The following is a recent presentation from Ericsson on HTML5 that gives a good idea on why it is a good idea.

HTML5 impact on application programming

View more presentations from Ericsson Labs.

Another interesting place to look for some HTML5 stuff is Patrick Chanezon's html5 Bookmarks

UEInformationRequest/UEInformationResponse - New RRC messages in Release-9

As is obvious from the title, The UE information procedure is used by E-UTRAN to request the UE to report information [1].

There are two different scenarios for the Network to send the UEInformationRequest message to the UE. One is to find out the number of RACH preambles it needed for the random access procedure and the other is to get the measurement information when a Radio Link Failure (RLF) occurred.

[2] also provides the following detail:

The network may poll for the UE report after a successful random access procedure (UEInformationRequest) and the UE responds with the number of preambles sent by MAC for the last successfully completed random access procedure and whether contention is detected by MAC for at least one of the transmitted preambles for the last successfully completed random access procedure (UEInformationResponse).

Source:

[1] 3GPP TS 36.331 V9.3.0: Radio Resource Control (RRC); Protocol specification - Section 5.6.5

[2] 3GPP TR 36.902 V9.2.0: Self-configuring and self-optimizing network (SON) use cases and solutions

Proximity Indication - New RRC Uplink Message in Rel-9

The inbound handover from a Macro eNB to an HeNB (a.k.a. Femtocell) is not supported in Release 8. Before making a handover decision to a HeNB, the Macro eNB needs to acquire UE measurement information related to the so-called target CSG cell. Nevertheless, UEs cannot continuously make measurements and read the system information of lots of CSG cells in cases of large scale HeNB deployments.

In order to allow the UE to make those measurements efficiently, a newly defined proximity report can be configured within the RRC Reconfiguration message. This proximity report will allow the UE to send a so-called “proximity indication” to the source eNB in the uplink whenever it is entering or leaving the proximity of one or more cells with CSG IDs that the UEs has in its CSG Whitelist.

A UE that is able to determine that it is near its CSG cell can thus inform the network to take the necessary actions for handover preparation. The detection of proximity is based on an autonomous search function.

The source eNB, upon receiving the proximity indication, might ask the UE to perform measurements of the CSG cell, to read the System Information (SI) or, in case it already has all required information, it might already start the handover procedure. PCI (Physical Cell Identification) confusion is resolved in Release 9. The eNB will ask the UE to report the global cell identity. As usual the UE reporting is using the RRC measurement procedures. The ovell procedure is illustrated in Figure below.

In summary five basic steps can be identified:

1. Proximity configuration/reporting

2. HO measurement configuration/reporting

3. Resolution of PCI confusion by requesting and reporting System Information

4. Access Control in the network

5. HO execution

Since the CSG search can be very slow there are no strict requirements on the inbound handover performance, which can range from one to several 10’s of seconds.

Since the proximity information is based on UE signaling, the network might be receiving a lot of proximity indications, increasing the network load. Therefore, it was agreed to limit proximity indications a UE can send within a certain time frame. A timer, called the prohibit proximity timer, was introduced.

Source:

• 3GPP TS 36.331 v9.3.0 section 5.3.14
• Nomor Research Whitepaper - LTE Home Node Bs and its enhancements in Release 9