2.6 GHz Spectrum & the Next Generation Mobile Broadband Networks



Please keep visiting for insights, analysis, discussions on wireless technologies, business and trends now at my new blogsite shahneil.com

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As the much awaited 2010 Mobile world Congress will kick in on 15th February in Barcelona, Spain, primary focus will be on discussing and showcasing the future of mobile broadband industry with cutting edge products, technologies highlighting m-commerce, m-marketing, m-advertisements, broadband deployment and initiatives broadening the mobile ecosystems.

“There is clear evidence that the volume of data flowing over mobile networks is growing rapidly and is being accelerated by the popularity of smart phones and the growth in music and video downloads,” said Tom Phillips, Chief Regulatory Affairs Officer at the GSMA.

With this unique and new view of the mobile landscape unfolding, one of the primary driver will be the utilization of ever scarce resource: Spectrum. The licensing of the 2.6 GHz spectrum will be vital in satisfying the demand for greater capacity for Mobile Broadband and launching next-generation networks such as LTE, which will start to be deployed commercially around the world this year .

As I mentioned in my previous article covering the WiMAX business model highlighting the importance of the spectrum and its contribution in the wireless operator’s cost model. Building on it we now know that the licensing of the 2.6 GHz band will be critical to unlocking the benefits of global scale economies in the Mobile Broadband market. The outcome of 2.6GHz allocation will have far-reaching consequences for how the adoption dynamics of WiMAX and 3GPP (such as HSPA and, in future, LTE) will play out in this region since 2.6GHz is the first arena where the two proponents will be battling each other in the same area of spectrum.

So let’s jump in discussing and analyzing about the 2.6GHz band its importance, what’s in store and bullet its implications on the future of mobile broadband. This analysis extends the scope of the report on 2.6 GHz band recently released by the GSMA & GVP. This report maybe biased towards LTE but lets draw some real pointers and analyze it.

Digging in about 2.6GHz band..

The 2.6 GHz band (2500-2690 MHz), sometimes also referred as the 2.5 GHz band, was allocated by the World Radio communication Conference (WRC) in 2000 for terrestrial mobile communications services. The 2.6GHz band is often referred to as the “IMT-2000 expansion band”(now !!) or the “3G expansion band”(earlier) and is 190MHz wide (substantial !!). This band has been allocated on primary basis to all the three ITU regions for terrestrial mobile communications compared to the smaller allocation of 3.5 GHz (3.4-4.2 GHz) Why ??

Note: ITU Regions: Region 1 comprises Europe, Africa, the Middle East west of the Persian Gulf including Iraq, the former Soviet Union and Mongolia; Region 2 covers the Americas, Greenland and some of the eastern Pacific Islands; Region 3 contains most of non-former-Soviet-Union Asia, east of and including Iran, and most of Oceania.

WRC imposed stringent power limits on satellite systems with limited geographic footprint operating in 2.6 GHz band shifting the importance of satellite systems more into 3.5 GHz bands. Also to add to this WRC-07 decided against the global identification for IMT, including WiMAX, in any part of the satellite C band (3.4-4.2 GHz)  with an exception of the mobile service allocation in 3.4-3.5 GHz thus making this band less globally harmonized for IMT. Hence the 2.6GHz band is now in a unique position to be exploited as a common band for commercial terrestrial mobile broadband access services on a global basis.

The beauty of the 190MHz wide spectrum is how it is to be divided for allocation. Should it be paired or unpaired suiting to corresponding FDD and TDD modes of operations.

The International Telecommunications Union (ITU) presents three possible options:

Option I: A mix of FDD(paired) and TDD(unpaired) spectrum plan which avoids interference problems this two different modes of operations

Option II: No unpaired spectrum included in this plan and leaves the second member of each pair undetermined

Option III: A Flexible plan on the amount of spectrum allocation for either of the paired(FDD) or unpaired(TDD) modes of the operation

The adoption of above plans differs from region to region, country to country and market to market depending upon the  technology Standard to be deployed either HSPA/HSPA+, LTE or WiMAX. A channel width of 20 MHz is recommended for most efficient use of current technology capabilities  for FDD (2×20 MHz) as well as TDD (a 20 MHz block is sufficient). Licensing should be based on a structure of 5 MHz channel blocks to allow support for 5,10, 15 or 20 MHz channels dependent on spectrum availability and each market’s competitive situation. Future technology evolution (4G) will most likely be based on combining multiple channels with 20 MHz being an ideal building block.

The ITU Option 1 band plan is well suited to meeting this goal by enabling technology neutrality and competitive ―4G‖wireless equipment choices for both FDD and TDD operation to mobile operators (including both LTE and WiMAX).There is widespread agreement at national levels as well as at the European Union and its Commission in adoption of Option 1 band plan.

Recent licensing carries a bias toward Option 1 with slight differences related to country-specific situations. More auctions are expected in Europe as well as in major emerging markets such as Brazil and South Africa. Substantial 2.6 GHz spectrum is licensed in the United States, although allocation and utilization are less than ideal for unique, nonreproducible historical reasons that predate the allocation of this band to mobile communications.

The ITU Option 2 band plan does not accommodate demand for unpaired spectrum and, therefore, violates the principle of technology neutrality (WiMAX)

The ITU Option 3 might lead to is likely to lead to multiple different national band plans and other challenges such as regulatory hurdles coupled with interference management and costs and availability of the equipment to match up in a customized way to the different national band plans. It increases the need for guard bands and could drive costs up for spectrum owners since they would need to negotiate with each other to make sure efficient coexistence and sacrifice spectrum to use as guard bands

2.6 GHz Spectrum implications:

Socio – Economic Implications

• Expanding the wireless mobile broadband to developed as well as developing nations  at affordable price points

• With a standardized spectrum bands and allocations plan allowing global harmonization will help drive economies of scale driving the costs down

• Standardization also enables easy and ready accessibility of the common services across many geographies.
• Economic reuse and sharing of existing physical and operational infrastructure  of the mobile operators reducing CAPEX (deployment costs)

• Proper Spectrum standardization and band plans options enables technology (FDD/TDD) and service neutralities  facilitating innovation and healthy competition between equipment, device, and applications and services vendors to the benefit of customers

• The widespread mobile broadband deployment and growth have potential benefits (employment, GDP) for developed economies and in fact more for emerging economies.

Technological Implications

• LTE and WiMAX can exploit 20 MHz of contiguous spectrum to deliver their highest spectral efficiency and highest throughputs. The 2.6 GHz band makes such allocation possible enabling the operators to operate high-speed LTE/WiMAX services at optimum performance.
• The 2.6 GHz frequencies have relatively short propagation ranges and inferior in-building penetration characteristics compared to lower frequencies makes it less suitable for rural areas( But with beam forming this can be taken care of..)
• On the other hand, the short propagation range and the large amounts of bandwidth (190 MHz) available in this band make it ideal for operators seeking to offer high network capacity and improve the speeds of mobile data transmission they can deliver to users in urban and suburban areas.
• Looking ahead, the shorter 2.6 GHz wavelengths can achieve greater improvements in performance through increased use and capabilities of smart antenna techniques such as MIMO and beam forming than is possible at lower frequencies. Thus, the gaps between environments in which 2.6 GHz can be used economically and efficiently relative to those where frequencies below 1 GHz are better suited may be somewhat reduced in favor of 2.6 GHz.
• The 2.6 GHz spectrum is the ideal complement to the 700 MHz spectrum, also known as ‘digital dividend’, and will enable the most cost-effective nationwide coverage of Mobile Broadband across both rural and urban environments. Also, LTE is likely to be of interest in other bands (e.g. 1800 MHz in Finland and Hong Kong).
• Though I mentioned at the start 2.6 GHz was seen as the “3G Extension band” but the ITU has changed its destination to the IMT band (for all mobile applications) positioning it strong for growth of 4G technologies (LTE Advanced & 802.16m).

2.6 GHz Adoption Facts:

• Recent licensing of this band in Hong Kong, Norway, Finland and Sweden, for example, has highlighted that there is more demand for paired (FDD) than unpaired spectrum (TDD) and that the ITU’s recommended Option 1 plan is the best structure to stimulate market growth in a technology-neutral and competitive environment. With an

• In the United States band plan, incumbents have the flexibility to deploy Time Division Duplex (TDD) or Frequency Division Duplex (FDD) anywhere in the band (Option 3) . Here the major spectrum owners are Sprint & Clearwire deploying TDD WiMAX which will be followed by future LTE rollouts by Verizon Wireless possibly in 700MHz band and AT&T is currently focusing on HSPA/HSPA+ networks to match up to WiMAX speeds.

• Governments in most Western European countries as well as in Brazil, Chile, Colombia, and South Africa are planning to award 2.6 GHz frequencies within the next two years.

Summarizing the benefits, implications, facts and the mobile broadband trends, 2.6 GHz spectrum ownership and band allocation can shape the business models for the next generation technologies. It will be a significant part in developing a wireless ecosystem which will offer high-speed mobile broadband solutions which shall  be easy to access, seamless across geographies and at an affordable price !!

- Neil Shah

References:

Unstrung.com Report : 2.6GHz Spectrum Key for LTE
Maravedis-bwa.com : Europe Prepares for 2.6 GHz spectrum Feeding Frenzy
Five bidders take 2.6 GHz WiMAX spectrum in Norway
GSMA & GVP Report on "The 2.6 GHz Spectrum Band"
WiMAX Forum 2.5 GHz Spectrum Manager
Light Reading : GSMA Wants More LTE Spectrum
3G Americas: LTE Global Deployments
WiMAX Vision.com4G battle looms in Europe at 2.6GHz

Location Based Services Part II: LBS Network Architectures

Please keep visiting for insights, analysis, discussions on wireless technologies, business and trends now at my new blogsite shahneil.com

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In the previous blog LBS Part I we discussed about the different Location technologies and their comparisons on different parameters with their advantages/disadvantages. Today we will see how these positioning technologies integrate with the network architecture in different Wireless Standards (3GPP, 3GPP2, OMA, WiMAX, LTE)

We will first start with categorizing the location services by their usage as follows:

The above four categories can be practically implemented in the way the MS communicates through the network with the location server.

The Wireless operators seeing the significant value in LBS delivering a solid ROI, the operator’s engineering team must select one of the two possible deployment methods.

It can be implemented in either Control Plane or User plane mode. Each has its own advantages and disadvantages. This “control-plane” approach, while highly reliable, secure, and appropriate for emergency services, is costly and in many cases, overkill for commercial location-based services. In both 3GPP & 3GPP2 an IP based approach known as “user-plane” allows network operators to launch LBS without costly upgrades to their existing SS7 network and mobile switching elements

Let us consider an LBS implementation architecture as an example in both the modes.

1. Control Plane Architecture

The Control plane architecture consists of following core entities:

• PDE/SMLC: Position Determination Entity/Serving Mobile Location Center -PDE facilitates determination of the geographical position for a target MS. Input to the PDE for requesting the position is a set of parameters such as PQoS (Position Quality of Service – Accuracy, Yield, Latency) requirements and information about the current radio environment of the Mobile Station (MS)
• MPC/GMLC: Mobile Positioning Center/Gateway Mobile Location Center – MPC serves as the point of interface to the wireless network for the position determination network. MPC serves as the entity which retrieves, forwards, stores, and controls position information within the position network. MPC selects the PDE to use in position determination and forwards the position estimate to the requesting entity or stores it for subsequent retrieval.
• LCS Client: LCS client is a logical entity that requests the LCS server to provide information on one or more target MS. LCS client being an logical entity can reside within a PLMN, or outside the PLMNs or even in the UE
• Geoserver, LBS applications, SCP Service Control point and content

In this configuration, the MPC/GMLC effectively serves as the intermediary and gateway between the applications, running in the Web services space, while the PDE/SMLC runs in the signaling space. It serves as a holding agent for subscriber location information working with MSC<->VLR<->HLR and facilitates push and pull transactions. A “push” transaction might be an application that locates a subscriber and delivers a message, perhaps about a sale at a store nearby, while a “pull” transaction would consist of the subscriber invoking a service, such as Find my Nearest ATM machine. The service set-up and communication is performed via traditional signaling network. The MPC/GMLC also serves as a place to perform general administration functions, such as authentication/security, privacy, billing, provisioning, and so on.

Let us consider an example of position request flow between different entities. This shows an network initiated location request from the LCS in C-plane LBS Architecture.

These type of requests initiated from network side are mostly for network performance measurements, emergency services or for push services querying the MS location.

2. User Plane Architecture

The User Plane consists of following entities:

PS: Position Server – PS provides geographic position information of a target MS to requesting entities. PS serves as the point of interface to the LCS server functionality in the wireless packet data network. PS performs functions such as accepting and responding to the requests for location estimate of a target MS, authentication, service authorization, privacy control, billing, and allocation of PDE resources for positioning.

PDE: Position Determination Entity

The User plane architecture is similar to control plane but does not include the full functionality of the MPC/GMLC. Instead it allows the handset to invoke services directly with the trusted location applications, via TCP/IP, leaving out traditional SS7 messaging altogether. A scaled-down version of the MPC/GMLC handles authentication/security for the user-plane implementation approach. This method is focused on pull transactions, where the subscriber invokes a location-sensitive service. However, push transactions are possible and supported through the limited MPC/GMLC function. The User plane involves following entities

Let us consider an example of position request flow between different entities. This shows a handset initiated location request from the LCS residing in MS in U-plane LBS Architecture.

These requests are initiated from mobile station mostly for location based search requests like restaurants, navigation or for pull services querying the position server.

3. OMA (Open Mobile Alliance) U-Plane Architecture

Open Mobile Alliance (OMA), a mobile communications industry forum is created to bring open standards, platform independence, and global interoperability to the LBS market. More than 360 companies are represented in OMA, including MNOs and wireless vendors, mobile device manufacturers, content and service providers, and other suppliers.

The OMA User Plane consists of following entities and protocols.

• MLP: Mobile Location Protocol: MLP is a protocol for querying the position of mobile station between location server and a location service client
• RLP: Roaming Location Protocol: RLP is a protocol between location servers while UE is roaming
• PCP: Privacy Checking Protocol: PCP is a protocol between location server and privacy checking entity

SUPL (Secure User Plane Location):

SUPL is developed by the Open Mobile Alliance. SUPL is a separate network layer that performs many LBS functions that would otherwise be governed within the C-Plane, and is designed to work with existing mobile Internet systems. With SUPL, MNOs can validate the potential of the LBS market with a relatively small budget and few risks.  SUPL utilizes existing standard to transfer assistance data and positioning data over a user plane bearer. SUPL is an alternative and complementary solution to existing 3GPP and 3GPP2 control plane architecture. SUPL supports all handset based and assisted positioning technologies. SUPL is data bearer independent.

SUPL architecture is composed of two basic elements: a SUPL Enabled Terminal (SET) and a SUPL Location Platform (SLP)

• SUPL Enabled Terminal (SET): The SET is a mobile device, such as a phone or PDA, which has been configured to support SUPL transactions.
• SUPL Location Platform (SLP): The SLP is a server or network equipment stack that handles tasks associated with user authentication, location requests, location-based application downloads, charging, and roaming.

SLP consists of following functional entities,

• SUPL Location Center (SLC) coordinates the operation of SUPL in the network and manages SPCs.
• SUPL Positioning Center (SPC) provides positioning assistance data to the SET and calculates the SET position.

The core strength of SUPL is the utilization, wherever possible, of existing protocols, IP connections, and data-bearing channels (GSM,GPRS,CDMA,EDGE or WCDMA). SUPL supports C-Plane protocols developed for the exchange of location data between a mobile device and a wireless network including RRLP (3GPP: Radio Resource LCS protocol) and TIA-8014(Telecommunications Industry Association 801-A, Position Determination Service for cdma2000). SUPL also supports MLP (Mobile Location Protocol) and ULP (UserPlane Location Protocol). MLP is used in the exchange of LBS data between elements such as an SLP and a GMLC, or between two SLPs; ULP is used in the exchange of LBS data between an SLP and an SET.

Let us consider an example of position request flow between different entities. This shows a SET initiated location request in OMA-SUPL U-plane LBS Architecture.

SUPL vs. C-Plane

Two functional entities must be added to the C-Plane network in order to support location services: a Serving Mobile Location Center (SMLC), which controls the coordination and scheduling of the resources required to locate the mobile device; and a Gateway Mobile Location Center (GMLC), which controls the delivery of position data, user authorization, charging, and more. Although simple enough in concept, the actual integration of SMLCs and GMLCs into the Control Plane requires multi-vendor, multi-platform upgrades, as well as modifications to the interfaces between the various network elements.

LBS through SUPL is much less cumbersome. The SLP takes on most of the tasks that would normally be assigned to the SMLC and GMLC, drastically reducing interaction with Control Plane elements. SUPL supports the same protocols for location data that were developed for the C-Plane, which means little or no modification of C-Plane interfaces is required. Because SUPL is implemented as a separate network layer, MNOs have the choice of installing and maintaining their own SLPs or outsourcing LBS to a Location Services Provider.

4. LBS Architecture in WiMAX

The WiMAX network architecture for LBS is based on the basic network reference model (NRM) specified by the WiMAX Forum. The model basically differentiates the network architecture into two separate business entities, (NAPs) Network Access Providers which provides radio access and infrastructure whereas (NSPs) Network Service Providers provides IP connectivity with subscription and service delivery functions.

The NAP is typically deployed as one or more access service networks (ASNs). The NSP is typically deployed as one or more Connectivity service network CSN(s). The NAP interfaces with the MS on one side and the CSN on the other.

Below shows the location request initiation from the application either located in device or network.

This is basically MS managed location service. The MS receives location requests from the applications and takes necessary measurements, and determines its location and provides it to the other requesting applications through upper layer messaging. The locations calculations at MS are aided by the periodic geolocation parameters broadcasted of the serving Base Station and the neighboring BS by the serving BS using layer 2 LBS-ADV message defined in IEEE 802.16-2009. The LBS-ADV message delivers the XYZ coordinates, the absolute and relative position of serving and neighboring BS allowing the MS to perform triangulation or trilateration techniques (either EOTDA or RSSI) and further aided by GPS to locate accurately. In this framework no major specific functional support for LBS is required in either the ASN or the CSN. Whereas in a network managed location service requires few functional entities to be added and enhancements to the network such as Location Requester, Location Server, Location Controller, and Location Agent.

Also, The WiMAX network architecture for LBS is designed to accommodate user plane, control plane, and mixed-plane location approaches. The big advantage of user plane location is that the LS can directly get to the MS, and signaling is minimized across the various reference points.  However, for this to the happen, the MS needs to have obtained an IP address and be fully registered with the LS, and application layer support is required in the MS.

In contrast, for the control plane location, the LS does not communicate directly with the MS, and hence there is no hard requirement for the MS to have obtained an IP address. In other words, the control plane location approach relies more on the L2 connectivity of the MS. However, the signaling costs are generally higher in control plane location as the signaling will have to traverse multiple reference points before measurements can be obtained.

The mixed plane method is nothing but the LS invoking both control plane measurements and user plane measurements at the same time. The LS can then perform a hybrid location solution by combining the measurements to get much better accuracy for the location fix. This approach is also fully supported in the WiMAX network. The trade-off here is that this method costs a whole lot more in terms of latency for the fix and the associated signaling, however this will translate to much better accuracy for the MS location indoors where an insufficient number of GPS satellites may be visible

5. LBS in LTE

LTE also generally supports the same types of positioning methods (Cell ID, A-GPS, mobile scan report-based, and hybrid) as in WiMAX. LTE offers user and control plane delivery of GPS assistance data; WiMAX chose to provide only user plane delivery. The rationale was that rapid IP session setup with the LS offered by WiMAX minimizes the need for a control plane solution. In WiMAX, authorization and authentication for LBS service is provided by the AAA, whereas in LTE the gateway mobile location center (GMLC) provides the equivalent functionality. The LTE Location Services specification  is  being developed under the current work plan and targeted for 3GPP Release 9.

This sums up the Location Based Services Architecture covering 3GPP, 3GPP2, WiMAX, LTE and OMA standards.

In the next Part we shall cover the Use Cases, Business Model with current and future trends for LBS.

- Neil Shah

References:

3GPP TS 23.271, “Functional Stage 2 Description of Location Services (LCS)”; http://www.3gpp.org/

Open Mobile Alliance, “Secure User Plane Location V 2.0 Enabler Release Package”; http://member.openmobilealliance.org/

Etemad, K., Venkatachalam, M., Ballantyne, W., Chen, B.,(2009)  “Location Services in WiMAX Networks”, IEEE Communications Magazine.

WiMAX Forum, “Protocols and Procedures for Location Based Services,” v. 1.0.0, May 2009.

OMA, O. M. (2007). Enabler Release Definition for Secure UserPlane for Location (SUPL) . OMA

Faggion, N., S.Leroy, & Bazin, C. (2007). Alcatel Location-based Services Solution. France.

3GPP2. (2000). Location-Based Services Systems LBSS: Stage 1 Description. 3GPP2 S.R0019 . 3GPP2.

3GPP. (2006). 3GPP TS 23.271 V7.4.0 Technical Specification Group Services and System Aspects Functional stage 2 description of Location Services (LCS) (Release 7).