AT&T upgrading to HSPA+ but will it ensure reliability??

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

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Stephen Lawson of IDG News Service recently mentioned in his article why AT&T needs to spend $5 Billion on its wireless network. I agree with him on this as AT&T has to catch up with the coverage offered by Verizon Wireless.

Though AT&T boasts of the fastest 3G Network and it might be too, but customer satisfaction and connection reliability index especially in urban areas are the two main reasons which might blur AT&T’s image. And with inclusion of bandwidth hungry smartphone (iPhone primarily) users in its portfolio, loading their networks and juicing out the backhaul, situation might get out of control for AT&T  unless they start acting on it. Apart from the loading the other important factor which I mentioned earlier is coverage which affects the reliability.

Issue 1: 3G Speed & Reliability Tests

AT&T’s 3G network is based on HSPA (High-Speed Packet Access) and an upgrade to HSPA+, a system designed to deliver as much as 7.2M bps (bits per second). Verizon uses EV-DO (Evolution-Data Optimized), which that carrier said offers as much as 1.4M bps in real-world performance. The speed of the network for individual subscribers depends on a variety of factors. But what matter here is the reliability along with the speed. The PC World test, conducted by Novarum last year, found mixed results for network speeds among AT&T, Verizon and Sprint but showed AT&T in last place for reliability in all 13 cities tested.

The above analysis puts light on The “reliability” score depicts the percentage of  the tests in which the service maintained an uninterrupted connection at a reasonable speed (faster than dial-up) for Verizon, Sprint and AT&T in 13 different cities.

Issue 2: CAPEX on wireless infrastructure

Recent reports from TownHall Investment Research depicts that AT&T is short on CAPEX behind key competitor Verizon and Sprint on its Wireless infrastructure. AT&T’s capital expenditures on its wireless network from 2006 through September 2009 totaled about $21.6 billion, compared with $25.4 billion for Verizon and $16 billion for Sprint (including Sprint’s investments in WiMax operator Clearwire). Over that time, Verizon has spent far more per subscriber: $353, compared with $308 for AT&T. Even Sprint has outspent AT&T per subscriber, laying out $310 for network capital expenditure. That investment shortfall has been the major cause of AT&T’s poor network performance, which has been reflected in tests by Consumer Reports and PC World

The other issue is AT&T invests more in its wired infrastructure than in its wireless network, even though the wireless business contributes a majority of the carrier’s profit. AT&T gets 57 percent of its operating income from wireless and only 35 percent from wired services, but wireless only gets 34 percent of the capital expenditures, with the wired network taking up 65 percent of that spending.

Issue 3: Backhaul Capacity

Along with invest in upgrades to HSPA 7.2 in the base stations, AT&T needs to remove the backhaul bottlenecks to accommodate high speed data in the core. The backhaul limiting the speeds is the primary concern  as I mentioned in my previous post for operators choosing the right backhaul solution considering the capex/opex. The $5 billion investment gap could expand to $7 billion because of the need for new backhaul capacity to link AT&T’s wireless network into the wired Internet.

Issue 4: Old Infrastructure

Another looming problem for AT&T is that its E911 emergency calling system, which works on its older GSM (Global System for Mobile communications) network, hasn’t been adapted to use 3G and is unlikely to make the migration soon. That means AT&T will have to maintain that old network for the foreseeable future, including possibly more capital investment for more power-efficient GSM equipment.

Solutions:

Hot on the heels of T-Mobile USA’s announcement that it upgraded its 3G footprint to HSPA 7.2, AT&T Mobility said it upgraded its own 3G cell sites across the country with HSPA 7.2 software. However, AT&T clarified that it is still working to deploy increased backhaul capacity to the sites, a job that it will continue into 2011. With this the customer experience will definitely get a boost with improvement in consistency in the data sessions access. So apart from base station upgrades and increasing backhaul capacity AT&T needs to add more number of  base stations especially in the urban areas where the user confidence level is shaky and expand their coverage.  AT&T has already started taking some smart steps by moving the 3G service to its longer range 850MHz radio band in the San Francisco area which seems to have helped coverage there, and the company will probably take that strategy nationwide while testing coverage in specific areas and “surgically” increasing capacity.

So the ball is in AT&T’s court and they have to act, spend and expand !!

-

Neil Shah

References:

Analyst: AT&T Needs to Spend US$5B to Catch up by Stephen Lawson, IDG News Service
A Day in the life of 3G: Mark Suvillan, PC World
AT&T plans to double 3G speeds Ian Paul, PC World
AT&T upgrades cell sites to HSPA7.2 software: by Phil Goldstein, Fiercewireless.com

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).

HSPA, EVDO, WiMax then LTE but what about the mobile backhaul??

With HSPA, EVDO maturing, WiMax getting deployed and LTE getting ready to buzz around, it is soon changing the way mobile phones will access the networks. The bandwidth hungry new services, applications and the non-stop touch clicks on your smart handhelds are eventually going to obsolete these mature 3G networks. Whereas, the 4G access networks are definitely envisioned to control this ever-increasing wireless broadband traffic but what bout the evolution of backhaul?? Is it ready? or is it going to be a major bottleneck analogous to the traffic jams seen if only one lane was operating out of a four lane expressway.

So, let’s have a closer look on how the mobile backhaul network is currently positioned.

The trend below depicts the exponential growth in asynchronous data demand for next 5 years.

Mobile Traffic Projections for the next 5 years

Over the next few years, “user experience” will still continue to rely on 3G (and in some regions on 2G) technology.But for the mobile operator, LTE/WiMax is already part of the game plan. Operators have to learn the technology, and its impact on their networks, applications and service offering. Though, service providers are seeking revenue and profit growth through new differentiated packet-based services. Many of these services, such as mobile Internet and mobile TV, require high bandwidth—and the current backhaul infrastructure is not optimized for handling such traffic. Hence, providers have to add backhaul capacity while keeping operational costs under control, a situation that is forcing carriers to migrate their access and core networks to the new 3G and 4G infrastructure.

There are three main transport technologies in the backhaul arena – fiber, copper and wireless point-to-point microwave.

The costs of backhaul form a significant part of service providers’ revenue accounting for three quarters of mobile transport costs and 25-30% of total operating expenses. The 2G infrastructure carried voice traffic through switched TDM (T1/E1 or SDH/SONET) or ATM. As with 3G/4G services, already  the bandwidth requirements have shot exponentially and to transport voice and data efficiently has been the need of the hour.

Basic requirements for a 4G Backhaul network:

1. Capacity: A single tail site should be scalable to 100Mbps+ capacities to avoid bottlenecks

2. Latency: A solution that supports 10msec or less end-to-end latency

3. All IP: Support IP traffic from head to tail.

Current migrating strategy is transporting Ethernet packets over point-to-point Microwave. Over 50% of all mobile backhaul deployments worldwide (and nearly 70% outside the U.S.A.), point-to-point microwave systems offer simple and cost efficient backhauling for voice and high-speed data services. That’s because point-to-point microwave supports higher data rates than traditional copper T1/E1 lines, it delivers between 25% and 60% more bits compared with similar TDM based systems, and easily overcomes the high cost and limited availability associated with fiber. Thus, operators can connect the TDM ports today, and gradually shift traffic to the Ethernet ports in the future. This shift can be done from remote, so no additional CAPEX or OPEX are needed. The industry has already established that the end game of next generation mobile backhaul networks is all-IP/Ethernet. Ethernet is not only more scalable, it also offers huge cost savings across the entire network value chain.

Ethernet cost savings per 1 Million subscribers

Also migrating to high capacity and lower latency Ethernet/All IP network, the systems should also support QoS aware Adaptive Coding and Modulation and Statistical Multiplexing. The former helps optimizing network for spectrum efficiency, increasing the radio capacity and  thus reducing cost/bit and latter in optimizing traffic management over the network reducing congestion and improving efficiency. An IP over Ethernet infrastructure has the advantage of the bandwidth growth curve of Ethernet moving from 10 Megabits per second (Mbps) to 10 Gigabits per second (Gbps) today and 100 Gbps in future. This coupled with the decreasing cost of Ethernet ports provides growth opportunities with increasing economies of scale.

Ethernet microwave Vs. TDM microwave equipment cost comparison

Thus, of the three backhaul technology options operators can choose from, wireless point-to-point microwave can deliver the best cost-performance features, bringing faster ROI and driving forward the proliferation of advanced mobile services in the LTE/WiMax era. But in the longer run a hybrid  solution of microwave, optical or IP/MPLS core might be seen as a balanced solution that might reduce the OPEX with improved scalability, higher bandwidth, lower latency and better efficiency. So operators pull up the socks and get ready for the great migration.

Also, a point to note with CISCO’s recent acquisition of Starnet Networks which makes it now one of the most dominant player in mobile backhaul solutions market.

From the recent news releases:

Verizon has committed to deploying fiber to 90% of the cell sites in its territory by 2013, closely following VZW’s LTE rollout schedule

Qwest plans to run fiber 7,500 to 17,000 cell sites in its territory

- Neil Shah

References:

“ATM to ALL IP”  Cost effective Network Convergence – Tellabs ’2009.

“LTE Backhaul Solutions”- Ceragon June 2009

Cable Backhaul: A towering OpportunityWebinar Harris Stratex Networks Nov’2009