MAPCON - Multi Access PDN Connectivity

On Monday, I read Bernard Herscovich, CEO, BelAir Networks saying the following in RCR Wireless:

Wi-Fi is obviously a way to offload data to alleviate congestion, but it also contributes to overall network profitability by delivering data at a lower cost per megabit that traditional macrocells. ABI Research estimates that carrier Wi-Fi can deliver data at 5% the cost of adding cellular capacity. Perhaps the most important driver, though, is the fact that, properly designed and architected, a carrier Wi-Fi network will deliver a consistently great user experience. The implications of that on attracting and retaining subscribers are obvious.

We've also seen cable operators taking advantage of their broadband HFC infrastructure to mount Wi-Fi APs throughout their coverage areas, offering free Wi-Fi as a sticky service to attract and retain home broadband subscribers.

At the GSMA Mobile Asia Congress, back in mid-November, 2010, KDDI's president and chairman explained that while they would be migrating to LTE, which would double their network capacity, data demand in Japan was forecast to increase by 15 times over the next five years. So LTE alone, he admitted, would not be enough. A few weeks before that, European operators, including Deutsche Telekom and Telefonica, were making similar statements at the Broadband World Forum in Paris.

It is clear that LTE alone will not be sufficient to meet ongoing mobile data demand. Technical innovation has resulted in huge capacity gains, but we're now at a point where additional bandwidth is more of a by-product of incremental spectrum. And, we all realize the finite nature of that resource. So, based on this new spectrum, LTE macrocells could deliver a 2 – 4X capacity increase. Meanwhile, ABI estimates that data capacity requirements are increasing 150% per year.

So, it's pretty clear that carriers are going to need more than just an LTE swap out to keep delivering a great user experience. They need to, as many already realize, augment their licensed spectrum with Wi-Fi. KT, the second largest mobile carrier in South Korea, claims to be offloading 67% of their mobile data traffic onto Wi-Fi. There may also be additional unlicensed spectrum made available, at least in the U.S. and the U.K., through the release of so-called white space spectrum, freed up through the switch from analog to digital TV.

It is obvious from the technology point of view that Multiple PDN connections would need to be supported when the UE is using LTE for part of data connection and Wi-Fi for other part. In fact these two (or multiple) connections should be under the control of the same EPC core that can help support seamless mobility once you move out of the WiFi hotspot.

One of the items in 3GPP Release-10 is to do with supporting of multiple Packet Data Networks (PDN) connections for a device. A Release-9 network and the UE can only support 3GPP access based connection via EPC. In Release-10 support for upto 1 non-3GPP access has been added.

FMC100044 specifies the following requirements:

• The Evolved Packet System supports the following scenarios: a single Operator offering both fixed and mobile access; different Operators collaborating to deliver services across both networks.
• The Evolved Packet System shall support the access of services from mobile network through fixed access network via interworking.
• The Evolved Packet System shall be able to support functions for connectivity, subscriber authentication, accounting, Policy Control and quality of service for interworking between the fixed broadband access and Evolved Packet Core.
• The Evolved Packet System shall optimize QoS and Policy management meaning that it shall offer minimal signalling overhead, while interworking between the fixed broadband access and Evolved Packet Core.
• The Evolved Packet System shall be able to provide an equivalent experience to users consuming services via different accesses.

The Rel-10 work item extends Rel-9 EPC to allow a UE equipped with multiple network interfaces to establish multiple PDN connections to different APNs via different access systems. The enhancements enable:

• Establishment of PDN connections to different APNs over multiple accesses. A UE opens a new PDN connection on an access that was previously unused or on one of the accesses it is already simultaneously connected to.
• Selective transfer of PDN connections between accesses. Upon inter-system handover a UE transfers only a subset of the active PDN connections from the source to the target access, with the restriction that multiple PDN connections to the same APN shall be kept in one access.
• Transfer of all PDN connections out of a certain access system. A UE that is simultaneously connected to multiple access systems moves all the active PDN connections from the source to target access, e.g. in case the UE goes out of the coverage of the source access.

This work also provides mechanisms enabling operator's control on routing of active PDN connections across available accesses.

The scope of the work is restricted to scenarios where the UE is simultaneously connected to one 3GPP access and one, and only one, non-3GPP access. The non-3GPP access can be either trusted or untrusted.

The design of the required extensions to Rel-9 EPC is based on TR 23.861 Annex A, that provides an overview of the changes that are expected in TS 23.401 and TS 23.402 for the UE to simultaneously connect to different PDNs via different access systems.

See Also:

3GPP TR 23.861: Multi access PDN connectivity and IP flow mobility

3GPP TS 22.278: Service requirements for the Evolved Packet System (EPS)

Old Blog post on Multiple PDN Connectivity

Simplified view of Heterogeneous Networks (HetNets)

A very simple picture explaining HetNets are,

To learn more about HetNet's, see my old blog post here or the Qualcomm video from yesterday here.

Qualcomm Video on LTE Advanced: Heterogeneous Networks

Wilson Street: What can femtocells do - the next big thing!

I have blogged about the Alcatel-Lucent (ALU) Femtocells in the past. Few months back I posted about their shift from using the term Femtocells to Small cells. To make everyone aware of this small cells they launched their Wilson Street experiment and are now producing some episodes to show how these small cells can play big part in everyday life.

The first two episodes are embedded below from Youtube.

The latest (3rd) episode is available on the Wilson Street Website here.

eMPS: Enhanced Multimedia Priority Service in Release-10 and beyond

The response to emergency situations (e.g., floods, hurricanes, earthquakes, terrorist attacks) depends on the communication capabilities of public networks. In most cases, emergency responders use private radio systems to aid in the logistics of providing critically needed restoration services. However, certain government and emergency management officials and other authorised users have to rely on public network services when the communication capability of the serving network may be impaired, for example due to congestion or partial network infrastructure outages, perhaps due to a direct or indirect result of the emergency situation.

Multimedia Priority Service, supported by the 3GPP system set of services and features, is one element creating the ability to deliver calls or complete sessions of a high priority nature from mobile to mobile networks, mobile to fixed networks, and fixed to mobile networks.

Requirements for the Multimedia Priority Service (MPS) have been specified in TS 22.153 for the 3GPP Release-9

The intention of MPS is to enable National Security/Emergency Preparedness (NS/EP) users (herein called Service Users) to make priority calls/sessions using the public networks during network congestion conditions. Service Users are the government-authorized personnel, emergency management officials and/or other authorized users. Effective disaster response and management rely on the Service User’s ability to communicate during congestion conditions. Service Users are expected to receive priority treatment, in support of mission critical multimedia communications.

LTE/EPC Release 9 supports IMS-based voice call origination by a Service User and voice call termination to a Service User with priority. However, mechanisms for completing a call with priority do not exist for call delivery to a regular user for a priority call originated by a Service User. MPS enhancements are needed to support priority treatment for Release 10 and beyond for call termination and for the support of packet data and multimedia services.

MPS will provide broadband IP-based multimedia services (IMS-based and non-IMS-based) over wireless networks in support of voice, video, and data services. Network support for MPS will require end-to-end priority treatment in call/session origination/termination including the Non Access Stratum (NAS) and Access Stratum (AS) signaling establishment procedures at originating/terminating network side as well as resource allocation in the core and radio networks for bearers. The MPS will also require end-to-end priority treatment in case of roaming if supported by the visiting network and if the roaming user is authorized to receive priority service.

MPS requirement is already achieved in the 3G circuit-switched network. Therefore, if the network supports CS Fallback, it is necessary to provide at least the same capability as 3G circuit switched-network in order not to degrade the level of voice service. In CS Fallback, UE initiates the fallback procedures over the LTE as specified in TS 23.272 when UE decides to use the CS voice service for mobile originating and mobile terminating calls. To achieve priority handling of CS Fallback, NAS and AS signaling establishment procedures, common for both IP-based multimedia services and CS Fallback, shall be treated in a prioritized way.

In Release-10, for LTE/EPC, the following mechanisms will be specified.

• Mechanisms to allocate resources for signaling and media with priority based on subscribed priority or based on priority indicated by service signaling.
• For a terminating IMS session over LTE, a mechanism for the network to detect priority of the session and treat it with priority.

In Release-10, for CS Fallback, the following mechanism will be specified:

• A mechanism to properly handle the priority terminating voice call and enable the target UE to establish the AS and NAS connection to fall-back to the GERAN/UTRAN/1xRTT.

For more information, see:

3GPP TR 23.854: Enhancements for Multimedia Priority Service (Release 10)

3GPP TS 22.153: Multimedia priority service (Release 10)

10 business models that rocked 2010

Very interesting read!

10 business models that rocked 2010 - by @nickdemey (boardofinnovation.com)

View more presentations from Board of Innovation (BOI).

3GPP Tutorials via 'The SpecTools'

Some of you may have noticed that the new and revamped 3GPP website have recently started offering 3GPP specs and features tutorials via The SpecTools. There is quite a lot of useful information and most of it is premium but a lot is free as well.

So the new starters or those wishing to refresh their knowledge feel free to check this out:

http://www.thespectool.com/3gpp/index.php

Heterogeneous LTE Networks and Inter-Cell Interference Coordination

An interesting paper that is more of a background to my earlier post here is available from Nomor Research and is embedded below.

Heterogeneous LTE Networks and Inter-Cell Interference Coordination

View more documents from Zahid Ghadialy.

This paper is available to download from here.

RAN mechanisms to avoid CN overload due to MTC

Machine-to-Machine (M2M) is the future and Machine-type communications (MTC) will be very important once we have billions of connected devices. I have talked in the past about the 50 Billion connected devices by 2050 and the Internet of Things.

One of the challenges of today's networks is to handle this additional signalling traffic due to MTC. One of the very important topics being discussed in 3GPP RAN meetings is 'RAN mechanisms to avoid CN overload due to MTC'. Even though it has not been finalised, its interesting to see the direction in which things are moving.

The above figure from R2-106188 shows that an extended wait time could be added in the RRC Connection Reject/Release message in case if the eNodeB is overloaded. The device can reattempt the connection once the wait time has expired.

In R2-110462, another approach is shown where Core Network (CN) is overloaded. Here a NAS Request message is sent with delay tolerant indicator a.k.a. low priority indicator. If the CN is overloaded then it can reject the request with a backoff timer. Another approach would be to send this info to the eNodeB that can do a RRC Connection Reject when new connection request is received.

All Documents from 3GPP RAN2 #72-bis are available here. Search for NIMTC for M2M related and overload related docs.

More Dilbert Humour on Cloud Computing

When I posted a Dilbert cartoon on the weekend, I expected lots of people to click on 'Not Useful' box at the bottom of the post. Honestly I got more response than I expected. Now with Cloud being talked about everywhere, I thought it would be worthwhile sticking some more old Dilbert Cloud crackers.

To combine fun with work, there are some links as well pointing to some recent Cloud based articles. Enjoy!

Ericsson CTO: cloud computing + mobile connectivity = mind-blowing innovation

Look up, it's the future: Learning to love 'the cloud'

CES2011: NEC dual-screen Android Cloud Communicator LT-W hands-on

How the Wikimedia Foundation is Using OpenStack to Build a Cloud Infrastructure

Security researcher uses Amazon cloud to hack WPA-PSK passwords

Data security must improve for the cloud to succeed

Efficiency drive will grow government outsourcing and cloud usage, says Ovum

Introducing Windows Azure

Source of Cartoons: http://dilbert.com/

SI on Signalling and procedure for interference avoidance for in-device coexistence

In order to allow users to access various networks and services ubiquitously, an increasing number of UEs are equipped with multiple radio transceivers. For example, a UE may be equipped with LTE, WiFi, and Bluetooth transceivers, and GNSS receivers. One resulting challenge lies in trying to avoid coexistence interference between those collocated radio transceivers. Figure 4-1 below shows an example of coexistence interference.

3GPP initiated a Study Item (SI) in Release-10 timeframe to investigate the effects of the interference due to multiple radios and signalling. This study is detailed in 3GPP TR 36.816 (see link at the end).

Due to extreme proximity of multiple radio transceivers within the same UE, the transmit power of one transmitter may be much higher than the received power level of another receiver. By means of filter technologies and sufficient frequency separation, the transmit signal may not result in significant interference. But for some coexistence scenarios, e.g. different radio technologies within the same UE operating on adjacent frequencies, current state-of-the-art filter technology might not provide sufficient rejection. Therefore, solving the interference problem by single generic RF design may not always be possible and alternative methods needs to be considered. An illustration of such kind of problem is shown in Figure 4-2 above.

The following scenarios were studied:

- LTE coexisting with WiFi

- LTE coexisting with Bluetooth

- LTE Coexisting with GNSS

Based on the analysis in SI, some examples of the problematic coexistence scenarios that need to be further studied are as follows:

- Case 1: LTE Band 40 radio Tx causing interference to ISM radio Rx;

- Case 2: ISM radio Tx causing interference to LTE Band 40 radio Rx;

- Case 3: LTE Band 7 radio Tx causing interference to ISM radio Rx;

- Case 4: LTE Band 7/13/14 radio Tx causing interference to GNSS radio Rx.

In order to facilitate the study, it is also important to identify the usage scenarios that need to be considered. This is because different usage scenarios will lead to different assumption on behaviours of LTE and other technologies radio, which in turn impact on the potential solutions. The following scenarios will be considered:

1a) LTE + BT earphone (VoIP service)

1b) LTE + BT earphone (Multimedia service)

2) LTE + WiFi portable router

3) LTE + WiFi offload

4) LTE + GNSS Receiver

The SI also proposes some ways of reducing the interference and is work in progress at the moment.

Reference: 3GPP TR 36.816 : Study on signalling and procedure for interference avoidance for in-device coexistence; (Release 10).

Dilbert Humour: Cloud Computing

Source: Dilbert

If you like these then please click 'Very Useful' or 'More like this' so that I know people find these useful.

For similar things follow the label: Mobile Humour.

LTE-Advanced (Rel-10) UE Categories

I blogged about the 1200Mbps of DL with LTE Advanced earlier and quite a few people asked me about the bandwidth, etc. I found another UE categories table in Agilent lterature on LTE-Advanced here.

The existing UE categories 1-5 for Release 8 and Release 9 are shown in Table 4. In order to accommodate LTE-Advanced capabilities, three new UE categories 6-8 have been defined.

Note that category 8 exceeds the requirements of IMT-Advanced by a considerable

margin.

Given the many possible combinations of layers and carrier aggregation, many configurations could be used to meet the data rates in Table 4. Tables 5 and 6 define the most probable cases for which performance requirements will be developed.

Refresher: LTE MAC Layer Protocol

This is following the RLC refresher post here. You can also view logs from real tests on a real LTE UE here.

3GPP LTE-MAC

View more presentations from praveenkmr78.

eICIC: Enhanced inter-cell interference coordination in 3GPP Release-10

Inter-cell interference coordination (ICIC) was introduced in Release-8/9 of the 3GPP LTE standards. The basic idea of ICIC is keeping the inter-cell interferences under control by radio resource management (RRM) methods. ICIC is inherently a multi-cell RRM function that needs to take into account information (e.g. the resource usage status and traffic load situation) from multiple cells.

Broadly speaking, the main target of any ICIC strategy is to determine the resources (bandwidth and power) available at each cell at any time. Then (and typically), an autonomous scheduler assigns those resources to users. Thus, from the Radio Resource Control perspective, there are two kind of decisions: (a) which resources will be allocated to each cell? and, (b) which resources will be allocated to each user?. Clearly, the temporality of such decisions is quite different. Whereas resources to users allocation is in the order of milliseconds, the allocation of resources to cells take much longer periods of time or can be fixed.

Static ICIC schemes are attractive for operators since the complexity of their deployment is very low and there is not need for new extra signaling out of the standard. Static ICIC mostly relies on the fractional reuse concept. This means that users are categorized according to their Signal-to-Noise-plus-Interference Ratio (SINR), that means basically according to their inter-cell interference, and different reuse factors are applied to them, being higher at regions with more interference, mostly outer regions of the cells. The total system bandwidth is divided into sub-bands which are used by the scheduler accordingly.

A simple way to explain ICIC is based on picture above. The users are divided into two categories, one is Cell Center User (CCU), and the other one is Cell Edge User (CEU). CCUs are the users distributed in the gray region of above figure, and CEUs are the users distributed in the above red, green and blue areas. CCU can use all the frequencypoints to communicate with the base station, while CEU must use corresponding specified frequency points to ensure orthogonality between different cells.

CEUs can be assigned a higher transmissionpower for the frequency reuse factor is greater than 1. The frequency points are not overlapped at the edges so the adjacent cell interference is small. CCU’s frequency reuse factor is 1; for the path loss is small and transmission power is low. Therefore the interference to the adjacent cells is not high either.

Dominant interference condition has been shown when Non-CSG/CSG users are in close proximity of Femto, in this case, Rel8/9 ICIC techniques are not fully effective in mitigating control channel interference, and hence, Enhanced interference management is needed At least the following issues should be addressed by any proposed solutions:

o Radio link monitoring (RLM)

o Radio Resource Management (including detection of PSS/SSS and PBCH)

o Interference from CRS

oo To PCFICH/PHICH/PDCCH

oo To PDSCH

o CSI measurement

o Interference from PDCCH masked with P-RNTI and SI-RNTI (for SIB-1 only) and associated PCFICH

As a result, from Release-10 onwards eICIC work was started. In Rel-10, two eICIC or Enhanced inter-cell interference coordination (also incorrectly referred to as Enhanced Inter-Cell Interference Cancellation) were being actively discussed. They are Time domain eICIC and autonomous HeNB power setting. More advanced ideas are being thought of beyong Rel-10 including Interference management techniques on carrier resolution ( optimally exploiting available Networks frequency assets (carriers in same or different bands) , combination with Carrier Aggregation; interference management schemes proposed both during LTE-Advanced Study Item phase, and during Rel-10 HetNet eICIC work.

From an earlier presentation in SON Conference:

eICIC:

- Effectively extends ICIC to DL control - time domain

- Requires synchronization at least between macro eNB and low power eNBs in its footprint

- No negative impact on legacy Rel 8 Use

Range Extension(RE)

- Refers to UE ability to connect and stay connected to a cell with low SINR

- Achieved with advanced UE receivers - DL interference cancellation (IC)

RE + eICIC technique:

– Eliminates coverage holes created by closed HeNBs

– Improves load balancing potential for macro network with low power eNBs and leads to significant network throughput increase

–Enables more UEs can be served by low power eNBs, which can lead to substantially higher network throughput

More details on eICIC is available in 3GPP CR's and TR's listed below:

• R1-105081: Summary of the description of candidate eICIC solutions, 3GPP TSG-WG1 #62, Madrid, Spain, August 23rd – 27th, 2010.
• R1-104942: Views on eICIC Schemes for Rel-10, 3GPP TSG RAN WG1 Meeting #62, Madrid, Spain, 23-27 August, 2010.
• R1-104238: eICIC Chairman’s note, 3GPP TSG RAN WG1 Meeting #61bis, Dresden, Germany, 28th June – 2nd July 2010.
• R1-103822: Enhanced ICIC considerations for HetNet scenarios, 3GPP TSG RAN WG1 #61bis Meeting, Dresden, Germany, June 28 – July 2, 2010.

You can also check out NTT Docomo's presentation on LTE Enhancements and Future Radio Access here.

Mobile Broadband Enablers in future

From a presentation by Huawei at the New Zealand Future Wireless Technologies Seminar. The presentation is available here.

Dilbert Humour: Face Recognition Apps

Source: http://www.dilbert.com/fast/2010-12-17/

Voice over LTE – a step towards future telephony (Ericsson Whitepaper)

The Fact boxes in the Appendix give a very good quick overview of how different technologies work with VoLTE.

Voice over LTE – a step towards future telephony

View more documents from Zahid Ghadialy

An Intellectual Property Rights Primer

Page 5-8 is a very good starting point to understand the IPR issues surrounding LTE.

The Essentials of Intellectual Property - Sep 2010

View more documents from Zahid Ghadialy.

An accompanying video and download information is available on Ericsson's website here.

HSPA and LTE carrier aggregation

Last week there were press releases about the Long Term HSPA Evolution. The only thing that got reported mostly is the 650Mbps peak rates. There are other interesting features in Release-11 that is covered in Nokia Siemens Networks presentation. Here is one of them:

The idea of aggregating multiple carriers to increase performance is included in both LTE and HSPA. A logical step to fully leverage existing HSPA deployments and future LTE deployments is to aggregate the capacity of both systems and tie them together into a single mobile system. The concept is illustrated in Figure 3.

The aggregation of LTE and HSPA systems enables the peak data rates of the two systems to be added together. It also allows for optimal dynamic load balancing between the two radios. A small number of active LTE and HSPA aggregation-capable devices is sufficient to exploit this load balancing gain, since the network can schedule these devices to carry more data on the radio that has lower instantaneous loading and less data on the radio with the higher load at any given moment.

Carrier aggregation is expected to have no impact on the core network.

Multicarrier and multiband HSPA aggregation

From NSN Whitepaper on HSPA Evolution:

HSPA Release 10 with 4-carrier HSDPA provides a peak downlink data rate of 168 Mbps using 2x2 MIMO (Multiple Input Multiple Output) over the 20 MHz bandwidth. This matches the LTE Release 8 data rates obtained using comparable antenna and bandwidth configurations. A natural next step for the HSPA Release 10 downlink is to further extend the supportable bandwidths to 40 MHz with 8-carrier HSDPA, doubling the Release 10 peak rate to 336 Mbps.

8-carrier HSDPA coupled with 4x4 MIMO doubles the peak rate again to reach 672 Mbps, see Figure 1. The evolution of HSPA beyond Release 10 will push the peak data rates to rival those provided by LTE Advanced.

In addition to increased peak rates, the aggregation of a larger number of carriers improves spectrum utilization and system capacity owing to inherent load balancing between carriers. Additional capacity gains from trunking and frequency domain scheduling will also be seen.

Typical spectrum allocations do not provide 40 MHz of contiguous spectrum. To overcome spectrum fragmentation, HSDPA carrier aggregation allows carriers from more than one frequency band to be combined. 3GPP Release 9 already makes it possible to achieve 10 MHz allocation by combining two 5 MHz carriers from different frequency bands, such as one carrier on 2100 MHz and another on 900 MHz.

The 4-carrier HSDPA of Release 10 extends this further, allowing the aggregation of up to four carriers from two separate frequency bands. Long Term HSPA Evolution allows eight carriers. Typical cases of HSDPA multiband aggregation are shown in Figure 2.

Packet Flow in 2.5G, 3G, 3.5G and 4G

The 'LTE Signaling' is a very interesting book just being released that is a must have for people who are involved in design, development and testing. A book that explains the basic concepts from beginning till advanced concepts and explains how different components and interfaces fit together.

Though I havent yet read this book, I have read the earlier one titled UMTS Signaling, from the same authors that is an excellent reference for understanding Signalling in UMTS. I have no doubt that this book will be the same high quality.

The Excerpt on Wiley's website provides complete chapter 1 which is quite detailed and the Packet flow pictures and details below is extracted from this book.

The first stage of the General Packet Radio Service (GPRS), that is often referred to as the 2.5G network, was deployed in live networks starting after the year 2000. It was basically a system that offered a model of how radio resources (in this case, GSM time slots) that had not been used by Circuit Switched (CS) voice calls could be used for data transmission and, hence, profitability of the network could be enhanced. At the beginning there was no pre-emption for PS (Packet Switched) services, which meant that the packet data needed to wait to be transmitted until CS calls had been finished.

In contrast to the GSM CS calls that had a Dedicated Traffic Channel (DTCH) assigned on the radio interface, the PS data had no access to dedicated radio resources and PS signaling, and the payload was transmitted in unidirectional Temporary Block Flows (TBFs) as shown in Figure 1.2.

In Release 99, when a PDP (Packet Data Protocol) context is activated the UE is ordered by the RNC (Radio Network Controller) to enter the Radio Resource Control (RRC) CELL_DCH state. Dedicated resources are assigned by the Serving Radio Network Controller (SRNC): these are the dedicated physical channels established on the radio interface. Those channels are used for transmission of both IP payload and RRC signaling – see Figure 1.7. RRC signaling includes the exchange of Non-Access Stratum (NAS) messages between the UE and SGSN.

The spreading factor of the radio bearer (as the combination of several physical transport resources on the Air and Iub interfaces is called) depends on the expected UL/DL IP throughput. The expected data transfer rate can be found in the RANAP (Radio Access Network Application Part) part of the Radio Access Bearer (RAB) assignment request message that is used to establish the Iu bearer, a GPRS Tunneling Protocol (GTP) tunnel for transmission of a IP payload on the IuPS interface between SRNC and SGSN. While the spreading factor controls the bandwidth of the radio connection, a sophisticated power control algorithm guarantees the necessary quality of the radio transmission. For instance, this power control ensures that the number of retransmitted frames does not exceed a certain critical threshold.

Activation of PDP context results also in the establishment of another GTP tunnel on the Gn interface between SGSN and GGSN. In contrast to IuPS, where tunnel management is a task of RANAP, on the Gn interface – as in (E)GPRS – the GPRS Tunneling Protocol – Control (GTP-C) is responsible for context (or tunnel) activation, modification, and deletion.

However, in Release 99 the maximum possible bit rate is still limited to 384 kbps for a single connection and, more dramatically, the number of users per cell that can be served by this highest possible bit rate is very limited (only four simultaneous 384 kbps connections per cell are possible on the DL due to the shortness of DL spreading codes).

To increase the maximum possible bit rate per cell as well as for the individual user, HSPA was defined in Releases 5 and 6 of 3GPP.

In High-Speed Downlink Packet Access (HSDPA) the High-Speed Downlink Shared Channel (HSDSCH) which bundles several High-Speed Physical Downlink Shared Channels (HS-PDSCHs) is used by several UEs simultaneously – that is why it is called a shared channel.

A single UE using HSDPA works in the RRC CELL_DCH state. For DL payload transport the HSDSCH is used, that is, mapped onto the HS-PDSCH. The UL IP payload is still transferred using a dedicated physical data channel (and appropriate Iub transport bearer); in addition, the RRC signaling is exchanged between the UE and RNC using the dedicated channels – see Figure 1.8.

All these channels have to be set up and (re)configured during the call. In all these cases both parties of the radio connection, cell and UE, have to be informed about the required changes. While communication between NodeB (cell) and CRNC (Controlling Radio NetworkController) uses NBAP (Node B Application Part), the connection between the UE and SRNC (physically the same RNC unit, but different protocol entity) uses the RRC protocol.

The big advantage of using a shared channel is higher efficiency in the usage of available radio resources. There is no limitation due to the availability of codes and the individual data rate assigned to a UE can be adjusted quicker to the real needs. The only limitation is the availability of processing resources (represented by channel card elements) and buffer memory in the base station.

From the user plane QoS perspective the two major targets of LTE are:

• a further increase in the available bandwidth and maximum data rate per cell as well as for the individual subscriber;

• reducing the delays and interruptions in user data transfer to a minimum.

These are the reasons why LTE has an always-on concept in which the radio bearer is set up immediately when a subscriber is attached to the network. And all radio resources provided to subscribers by the E-UTRAN are shared resources, as shown in Figure 1.9. Here it is illustrated that the IP payload as well as RRC and NAS signaling are transmitted on the radio interfaces using unidirectional shared channels, the UL-SCH and the Downlink Shared Channel (DL-SCH). The payload part of this radio connection is called the radio bearer. The radio bearer is the bidirectional point-to-point connection for the user plane between the UE and eNodeB (eNB). The RAB is the user plane connection between the UE and the Serving Gateway (S-GW) and the S5 bearer is the user plane connection between the S-GW and public data network gateway (PDN-GW).

The end-to-end connection between the UE and PDN-GW, that is, the gateway to the IP world outside the operator’s network, is called a PDN connection in the E-UTRAN standard documents and a session in the core network standards. Regardless, the main characteristic of this PDN connection is that the IP payload is transparently tunneled through the core and the radio access network.

To control the tunnels and radio resources a set of control plane connections runs in parallel with the payload transport. On the radio interface RRC and NAS signaling messages are transmitted using the same shared channels and the same RLC transport layer that is used to transport the IP payload.

RRC signaling terminates in the eNB (different from 3G UTRAN where RRC was transparently routed by NodeB to the RNC). The NAS signaling information is – as in 3G UTRAN – simply forwarded to the Mobility Management Entity (MME) and/or UE by the eNB.

You can read in detail about all these things and much more from the Wiley's website here.

The Innovation Driving Femto-powered Small Cells

Intelligence: the Innovation Driving Femto-powered 
Small Cells

View more presentations from Ubiquisys Femtocell.

Slideshow as presented by Richard Staveley from Ubiquisys at Femtocell Americas 2010.

SON in Heterogeneous Networks

Another presentation from the SON 2010 Conference based on yesterdays theme of HetNets.

SON in Heterogeneous Networks from Zahid Ghadialy

Presented by Seungpyo Hong of Institute of Network Technology, SK Telecom.

What are Heterogeneous Networks (HetNets)?

HetNets are hot. I hear about them in various contexts. Its difficult to find exactly what they are and how they will work though. There is a HetNets special issue in IEEE Communications Magazine coming out next year but that's far away.

I found an interesting summary on HetNets in Motorola Ezine that is reproduced below:

“The bigger the cell site, the less capacity per person you have,” said Peter Jarich, research director with market intelligence firm Current Analysis. “If you shrink coverage to a couple of blocks, you are having that capacity shared with a fewer number of people, resulting in higher capacity and faster data speeds.”

This is a topic the international standards body, the Third Generation Partnership Project (3GPP), has been focusing on to make small cells part of the overall cellular network architecture.

“What we’re seeing is a natural progression of how the industry is going to be addressing some of these capacity concerns,” said Joe Pedziwiatr, network systems architect with Motorola. “There is a need to address the next step of capacity and coverage by introducing and embracing the concepts of small cells and even looking at further advances such as better use of the spectrum itself.”

As such, discussion regarding this small-cell concept has emerged into what is called heterogeneous networks, or Het-Net, for short. The idea is to have a macro wireless network cooperating with intelligent pico cells deployed by operators to work together within the macro network and significantly improve coverage and augment overall network capacity. Small cells can also be leveraged to improve coverage and deliver capacity inside buildings. Indoor coverage has long been the bane of mobile operators. Some mobile operators are already leveraging this concept, augmenting their cellular service offering with WiFi access to their subscriber base in order to address the in-building coverage and capacity challenges facing today’s cellular solutions.

Pedziwiatr said this Het-Net structure goes far beyond what is envisioned for femtocells or standard pico cells for that matter. Introducing a pico cell into the macro network will address but just one aspect of network congestion, namely air interface congestion. The backhaul transport network may become the next bottleneck. Finally, if all this traffic hits the core network, the congestion will just have shifted from the edge to the core.

“This requires a system focus across all aspects of planning and engineering,” Pedziwiatr said. “We’re trying to say it goes beyond that of a femto. If someone shows up at an operator and presents a pico cell, that is just one percent of what would be needed to provide true capacity relief for the macro network.”

Femtocells, otherwise known as miniature take-home base stations, are obtained by end users and plugged into a home or office broadband connection to boost network signals inside buildings. A handful of 3G operators worldwide are selling femtocells as a network coverage play. For the LTE market, the Femtocell Forum is working to convince operators of the value of a femtocell when it comes to better signal penetration inside buildings and delivering high-bandwidth services without loading the mobile network. This is possible, because the backhaul traffic runs over the fixed line connection. However, this femtocell proposition largely relies on end user uptake of them—not necessarily where operators need them, unless they install femtocells themselves or give end users incentives to acquire them.

As with any new concept, there are challenges to overcome before Het-Nets can become reality. Het-Nets must come to market with a total cost of ownership that is competitive for an operator to realize the benefit of providing better capacity, higher data speeds, and most of all, a better end-user experience said Chevli.

“The level of total cost of ownership has to be reduced. That is where the challenge is for vendors to ensure that any new solution revalidates every existing tenet of cellular topology and evolve it to the new paradigm being proposed,” Chevli said. “You can’t increase the number of end nodes by 25X and expect to operate or manage this new network with legacy O&M paradigms and a legacy backhaul approach.”

One of the issues is dealing with interference and Het-Net network traffic policies. “How do you manage all of these small cell networks within the macrocell network?” asked Jarich. “Right now if you have a bunch of femtocells inside a house, there is this concept that the walls stop the macrocell signals from getting in and out. You get a separation between the two. Go outdoors with small cells underlying bigger cells and you get a lot more interference and hand-off issues because devices will switch back and forth based on where the stronger signal is.”

Pedziwiatr said for a Het-Net to work, it would require a change in node management, whereby an operator isn’t burdened with managing big clusters of small cells on an individual basis. “We see elements of SON (self organizing networks), self discovery and auto optimization that will have to be key ingredients in these networks. Otherwise operators can’t manage them and the business case will be a lot less attractive,” he said.

Fortunately, the industry has already been working with and implementing concepts of SON in LTE network solutions. In the femtocell arena also, vendors have been incorporating some elements and concepts of SON so that installing them is a plug-and-play action that automatically configures the device and avoids interference. But even then, Het-Nets will require further SON enhancement to deal with new use cases, such as overlay (macro deployment) to underlay (pico deployments) mobility optimization.

When it comes to LTE, SON features are built into the standard, and are designed to offer the dual benefit of reducing operating costs while optimizing performance. SONs will do this by automating many of the manual processes used when deploying a network to reduce costs and help operators commercialize their new services faster. SON will also automate many routine, repetitive tasks involved in day-to-day network operations and management such as neighbor list discovery and management.

Other key sticking points are deployment and backhaul costs. If operators are to deploy many small cells in a given area, deploying them and backhauling their traffic should not become monumental tasks.

Chevli and Pedziwiatr envision Het-Nets being deployed initially in hot zone areas – where data traffic is the highest – using street-level plug-and-play nodes that can be easily installed by people with little technical know-how.

“Today, macro site selection, engineering, propagation analysis, rollout and optimization are long and expensive processes, which must change so that installers keep inventories of these units in their trucks, making rollout simple installations and power-ups,” said Pedziwiatr. “These will be maintained at a minimum with quick optimization.”

The notion of backhauling traffic coming from a large cluster of Het-Net nodes could also stymie Het-Nets altogether. Chevli said that in order to keep costs down, Het-Net backhaul needs to be a mix of cost-effective wireless or wired backhaul technology to aggregate traffic from what likely will be nodes sitting on lamp posts, walls, in-building and other similar structures. The goal then is to find a backhaul point of presence to aggregate the traffic and then put that traffic on an open transport network in the area.

Backhaul cost reductions may also be a matter of finding ways to reduce the amount of backhaul forwarded to the core network, Pedziwiatr said. These types of solutions are already being developed in the 3G world to cope with the massive data traffic that is beginning to crush networks. For traffic such as Internet traffic, which doesn’t need to travel through an operator’s core network, offloading that traffic as close to the source as possible would further drive down the cost of operation through the reduction of backhaul and capacity needs of the core network.

In the end, with operators incorporating smaller cells as an underlay to their macro network layer rather than relying on data offloading techniques such as femtocells and WiFi that largely depend on the actions of subscribers and impacted by the surrounding cell operating in the same unlicensed frequency, Het-Nets in licensed spectrum will soon become the keystone in attacking the ever-present congestion issue that widely plagues big cities and this is only likely to get worse over time.

Image Source: Dr. Daichi Imamura, Panasonic presentation.

Refresher: LTE RLC Layer Protocol

LTE RLC Layer Protocol

View more presentations from All About 4G.

6LoWPAN: Low power Wireless Personal Area Networks

From Wikipedia: 6lowpan is an acronym of IPv6 over Low power Wireless Personal Area Networks, or (as the "personal" qualification is no longer relevant), IPv6 over LoW Power wireless Area Networks. 6lowpan is the name of a working group in the internet area of the IETF. The 6lowpan group has defined encapsulation and header compression mechanisms that allow IPv6 packets to be sent to and received from over IEEE 802.15.4 based networks. IPv4 and IPv6 are the work horses for data delivery for local-area networks, metropolitan area networks, and wide-area networks such as the Internet.

There is a book from Wiley entitled "6LoWPAN: The Wireless Embedded Internet", which has a good definition and explanation of 6LoWPAN that I am using below. Wiley has excerpt from the book that details the complete introductory chapter.

As the Internet of routers, servers and personal computers has been maturing, another Internet revolution has been going on – The Internet of Things (see pic below). The vision behind the Internet of Things is that embedded devices, also called smart objects, are universally becoming IP enabled, and an integral part of the Internet. Examples of embedded devices and systems using IP today range from mobile phones, personal health devices and home automation, to industrial automation, smart metering and environmental monitoring systems. The scale of the Internet of Things is already estimated to be immense, with the potential of trillions of devices becoming IP-enabled. The impact of the Internet of Things will be significant, with the promise of better environmental monitoring, energy savings, smart grids, more efficient factories, better logistics, better healthcare and smart homes.

The Internet of Things can be understood as a layer of digital information that covers the physical world. Objects and places become part of the Internet of Things in two ways: First, data and information can be associated with a particular location, using geo-coordinates or a street address. Second with sensors and RFID tags or transmitters installed in these objects allowing then to be accessed via Internet protocols.

Remember, Ericsson has already predicted 50 Billion connected devices by 2050. See here.

The Institute of Electrical and Electronics Engineers (IEEE) released the 802.15.4 lowpower wireless personal area network (WPAN) standard in 2003, which was a major milestone, providing the first global low-power radio standard. Soon after, the ZigBee Alliance developed a solution for ad hoc control networks over IEEE 802.15.4, and has produced a lot of publicity about the applications of wireless embedded technology. ZigBee and proprietary networking solutions that are vertically bound to a link-layer and application profiles only solve a small portion of the applications for wireless embedded networking. They also have problems with scalability, evolvability and Internet integration.

The IEEE 802.15.4 standard released in 2003 was the biggest factor leading to 6LoWPAN standardization. For the first time a global, widely supported standard for lowpower wireless embedded communications was available [IEEE802.15.4]. The popularity of this new standard gave the Internet community the needed encouragement to standardize an IP adaptation for such wireless embedded links.

The ideal use of 6LoWPAN is in applications where:

• embedded devices need to communicate with Internet-based services,

• low-power heterogeneous networks need to be tied together,

• the network needs to be open, reusable and evolvable for new uses and services, and

• scalability is needed across large network infrastructures with mobility.

Connecting the Internet to the physical world enables a wide range of interesting applications where 6LoWPAN technology may be applicable, for example:

• home and building automation

• healthcare automation and logistics

• personal health and fitness

• improved energy efficiency

• industrial automation

• smart metering and smart grid infrastructures

• real-time environmental monitoring and forecasting

• better security systems and less harmful defense systems

• more flexible RFID infrastructures and uses

• asset management and logistics

• vehicular automation

One interesting example application of 6LoWPAN is in facility management, which is the management of large facilities using a combination of building automation, asset management and other embedded systems. This quickly growing field can benefit from 6LoWPAN, is feasible with today’s technology, and has real business demand.

You can read more from the book on Wiley's website here.

More information on purchasing and reviews on Amazon's website below:

The silent heroes of the wireless world

Often you will hear about some famous people from certain organisations who speak at conferences and meetings but there are often in the background many people who labour to ensure that reports, documents, presentations and technology are completed without problems.

Last Friday, I met up with some old colleagues who are these silent movers and shakers in our mobile industry. Often behind multiple monitors and pile of documents, these people work on the cutting edge future technologies. It was nice to know that they do read and refer to my blog from time to time and find it useful.

I should also like to mention the people who often mail me to thank me for the blog and the 3g4g website. I do quite often bump into people who know me for my work but dont know me personally. Sometimes they do get a bit surprised because my HQ (humour quotient) is very high. I have a jokelist active since 1999 and even though I dont get enough time to post jokes I do make it a point to keep it alive.

I am fortunate enough to learn a lot from such people, as knowledge is limitless and there is always something everyone can contribute as they may know it much better than others.

So please feel free to say hello to me when you come across me in any conference, presentation, party or even interviews. Its always good to know people.