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10 Cloud-Centric advances with LTE

With the advent of the iPhone and iPad – new classes of devices were born, one that captivates the imagination and capabilities of the common man. The devices now are always on, power hungry and data hungry – one that brings convergence of a multimedia and a computer married together. Hence, NGMN (a consortium of Operators) and 3GPP laid a foundation way back in 2006 for LTE and LTE-advanced standards development that have started to take off in a big way from mid-2010 onwards with the rollout of LTE (read Data Centric) networks. So what has changed from the UMTS world? How and why is it so different that operators will need to upgrade their networks, which is capital intensive? All these and more on how inadvertently we are moving to Cloud centric systems, sans the hoopla about iCloud, Amazon web-services or Hadoop.  Let us look at the problems and resolutions with LTE for moving our applications to the cloud and beyond.

Flatter Architecture and Air Interface developments (read lower Latency)

Problem

Latency and Round trip times over GERAN and UTRAN was always a performance bottleneck.

Solution

Flatter architecture with some of the functions of the RNC moving to the eNodeB & MME along with a complete re-designs of the air interface with OFDMA replacing W-CDMA air interface.

Air Interface

 

 Architecture

  

3GPP 36 series – http://www.3gpp.org/ftp/Specs/html-info/36-series.htm

Latency

  

Source: Nokia Research

All–IP (with IMS)

Problem

TDM & ATM have lower capacity/high cost for backhaul and transport.

Solution

LTE is the true all-IP mobility Technology where IP is supported ground up, from the eNodeB to all the nodes northbound. And IMS sits well with LTE as it is the preferred solution for voice over LTE. Another initiative called the SRVCCC (Single Radio Voice Call Continuity) 3GPP TS 23.216 specifies allows IMS session continuity when the terminal is Single Radio, thus only one RAT can be active at a time. So when moving out from IMS Voice capable LTE coverage, SRVCC allows UE voice continuity via handover to 2G/3G CS. It builds upon ICS, so it relies on the SCC AS to anchor the call and perform the call transfer between LTE and WCDMA/GSM CS access domains. It also needs a new interface between the Evolved Packet Core and the CS Core, the Sv interface, so the MME can request the MSC-S to reserve the necessary WCDMA/GSM CS resources before handover execution.

Guaranteed QOS

Problem

End-to-end QOS definition for various services from RAN to Core was insufficiently specified for 2G/3G.

Solution

The LTE air interface scheduler is responsible for dynamically allocating DL and UL air interface resources among the bearers appropriately while maintaining their desired QoS level in both DL and UL directions.

LTE bearers:

Guaranteed bit rate (GBR): Dedicated network resources related to a GBR value associated with the bearer are permanently allocated when a bearer becomes established or modified.

 Non-guaranteed bit rate (non-GBR): A service utilizing a non-GBR bearer may experience A non-GBR bearer is referred to as the default bearer, which is also used to establish IP connectivity. Any additional bearer(s) is referred to as a dedicated bearer and can be GBR or non-GBR.

 

Seamless HO

Problem

Inter-RAT mobility solutions and backward compatibility issues resolved by 3GPP and 3GPP2

Solution

An important feature of LTE is support for seamless mobility across eNodeBs and across MME/GWs. Fast and seamless handovers (HO) is particularly important for delay-sensitive services such as VoIP. The handovers occur more frequently across eNodeBs than across core networks because the area covered by MME/GW serving a large number of eNodeBs is generally much larger than the area covered by a single eNodeB. The signaling on X2 interface between eNodeBs is used for handover preparation. The S-GW acts as anchor for inter- eNodeB handovers. Also developing HO standards like MIP and 802.21 are used in mobile IP communications are Mobile IP and Sea Moby an evolving standard in IP based mobility. Mobile IP (MIP) is where a Home agent (HA) and foreign agent (FA) are used to seamlessly handover between two networks with an anchor IP address at the FA, with a Care-of-address generated at this location.

Two types of MIPs are supported as standards in many of the networks –

Client Mobile IP:  Each device supports a local Mobile IP client that interacts with HA via FA so that incoming data can be successfully routed by HA to the device.

Proxy Mobile IP:  Instead of having a Mobile IP client on the device, an instance of this is created in the ASN (in WiMAX).  Proxy MIP eliminates the constraint of requiring Mobile IP client on the WiMAX device. Proxy MIP allows MIP registration which takes place by the DAP/CAPC on behalf of the Client/CPE.

 

 

HenB Development (Femtocells)

Problem

Indoor coverage and traffic offload solutions for capacity and improved user experience.

Solution

Though the femtocell development has grown organically over the years from the initial 2G Pico/Femto cells, it has grown into a full blown solution with variants with release 10 from 3GPP (SIPTO/LIPA/IFOM) 3GPP TR 23.861 . Femto forum has approved 3 different architectures variants for operators to use for their deployment, from 3GPP TR 23.830.

  

 The variant 1 provides benefits for the operators that already have a 3G HeNB solution and wish to migrate towards LTE HeNB. This architectural variant is similar to 3G Home Node B architecture terminating both control plane and user plane in the Gateway. The variant 2 provides the main benefit in deployment scenarios where the number of HeNBs is rather limited or scattered within the network with reduced cost effect, so that the number of the HeNBs per MME is not causing any scalability issues, with SCTP/GTP-U connections maintenance. When total number of HeNB increases, as from scenario 1 to scenario 2 or from scenario 2 to scenario 3, an obvious impact with variant 3 is the increased requirement on scalability of S-GW. The highest resource requirement on S-GW to manage large number of HeNBs comes from processing of GTP-echo mechanism, but the impact of additional UDP and GTP contexts must also be considered.

MIMO

Problem

Radio propagation channel is characterized by multipath propagation due to scattering on different obstacles.

Solution

MIMO (Multiple Input Multiple Output) is an antenna technology that is used both in transmission and receiver equipment for wireless radio communication. There can be various MIMO configurations. MIMO takes advantage of multi-path and uses multiple antennas to send multiple parallel signals (from transmitter). In an urban environment, these signals will bounce off trees, buildings, etc. and continue on their way to their destination (the receiver) but in different directions. “Multi-path” occurs when the different signals arrive at the receiver at various times. With MIMO, the receiving end uses an algorithm or special signal processing to sort out the multiple signals to produce one signal that has the originally transmitted data.

  

  

 

Improvements from MIMO 

IPV6 (dual stack devices)

Problem

TCP/IP over GERAN and UTRAN was always a performance bottleneck due to protocol conversion happening at the transport layer.

Solution

Advantages of IPv6 include:

  • Simplified header processing (ROHC)
  • Less fragmentation of the address space, leading to smaller routing tables.
  • Built-in support for Mobile IP
  • Support for route optimization in Mobile IP.
  • Support for address auto-configuration.
  • Reduced dependency on translation devices.
  • More sophisticated flow identification, potentially leading to improvements in QoS support

Dual Stack Device

The growth of the wireless industry (both cellular and wireless networks based on protocols such as 802.11x, 802.16, 802.20, UMTS, UWB, MIMO, etc.) has been nothing short of phenomenal. In some countries, such as Italy and Great Britain, the number of cell phones actually exceeds the number of people. In this world of continuous reachability and reliance on the ability to access information at any time, the mobility requirements for end users have become exceptionally important. From the carriers’ perspective, especially those supporting multiple media access types (e.g. 3G and WiMax), leveraging IP as the method of transporting and routing packets makes sense. Cell phones and PDAs can already access the Internet, play games with other users, make phone calls, and even stream video content. Instead of supporting all of these functions using different transport protocols and creating intermediary applications to facilitate communicatieNodeBs and across MME/GWs. Fast and seamless handovers (HO) is particularly important for delay-sensitive services such as VoIP. The handovers occur more frequently across eNodeBs than across core networks because the area covered by MME/GW serving a large number of eNodeBs is generally much larger than the area covered by a single eNodeB. The signaling on X2 interface between eNodeBs is used for handover preparation. The S-GW acts as anchor for inter- eNodeB handovers. Also developing HO standards like MIP and 802.21 are used in mobile IP communications are Mobile IP and Sea Moby an evolving standard in IP based mobility. Mobile IP (MIP) is where a Home agent (HA) and foreign agent (FA) are used to seamlessly handover between two networks with an anchor IP address at the FA, with a Care-of-address generated at this location.

DPI (Deep Packet Inspection)

Problem

Traffic shaping and tailoring services to reduce throttle the bandwidth hogs as well as from peer-to-peer traffic.

Solution

Deep Packet Inspection (DPI) is the technology that refers to devices and technologies that inspect and take action based on the contents of the packet “payload” rather than just the packet header. Once DPI algorithms determine what content is in the payload, traffic information can be logged and actions triggered in network elements as necessary depending on the application. These functions need to happen in real-time in order to evaluate and act on service heuristics or generate billing information.

Managing Traffic: DPI enables traffic throttling, blocking at a flow or application level. This has become especially important as bandwidth-hungry, priority-packet multi-media usage has skyrocketed, mainly in the form of Voice over IP (VoIP) and video/audio over IP.

Secure quality-of-service for premium services: Helps traffic generated by best-effort services as the quality-of-service class implies, be deferred or even rejected if buffers are overloaded.

Evaluate subscriber preferences for targeted marketing:  Subscribers accessing a specific type of content are more likely to be interested in associated products and services, than the general public. If the traffic concerned is identified by means of packet inspection, there could be opportunities for targeted marketing and injection of advertisements.

Improve network security: Network security is another area affected by peer-to-peer applications.

CALEA: DPI enables operators to meet the requirements of the Communications Assistance for Law Enforcement Act (CALEA) and its international equivalents to ensure that security services can use equipment for surveillance, in particular for VoIP traffic.

Copyright enforcement:  DPI can help enforce copyrights for content copyright owners or content protected by courts or official policy.

Distributed Baseband (COMP)

Problem

Deadzones for Radio coverage is an old problem and to get a new site to cover it has many complex steps – zoning, construction, etc.

Solution

Sites with smaller footprints, requiring no zoning or strand mounted outdoor cells (neighborhood area networks) along with software defined radio. Coordinated multi-point transmission/reception (CoMP) a solution by 3GPP, will be used as a tool to improve coverage, cell-edge throughput, and/or system efficiency. The main idea of CoMP is as follows – when an UE is in the cell-edge region, it may be able to receive signal from multiple cell sites and the UE’s transmission may be received at multiple cell sites. Given that, if we coordinate the signaling transmitted from the multiple cell sites, the DL performance can be increase significantly. This coordination can be simple as in the techniques that focus on interference avoidance or more complex as in the case where the same data is transmitted from multiple cell sites. For the UL, since the signal can be received by multiple cell sites, if the scheduling from the different cell sites, the system can take advantage of this multiple reception to significantly improve the link performance.

   (a)A coordinated beamforming and scheduling is done between cells to reduce the interference caused to other cells.

(b) Joint transmission by multiple cells to a given UE, in which they transmit at the same time using the same time and frequency radio resources, and dynamic cell selection, in which cells can be selected at any time in consideration of interference, are being studied. For joint transmission, two methods are being studied: non-coherent transmission, which uses soft-combining reception of the OFDM signal; and coherent transmission, which does precoding between cells and uses in-phase combining at the receiver.

M2M / Smart-grid

Problem

Controlling devices from the Cloud – a network reality or science fiction?

Solution

The communications industry and consumers are evolving through different phases:

  • Initially, people communicating with people (phones, smartphones)
  • Now, people communicating with machines (cloud computing)
  • Evolving to machines communicating with machines (hospital devices with computers)

These additional forms of communication are in addition to those occurring today on 3G WCDMA/HSPA networks, and will occur very rapidly on new LTE networks. Therefore, it is important that Machine-to-Machine (M2M) is implemented on both 3G and LTE networks, and that these networks and devices are interoperable. M2M devices such as sensors or meters are used to capture events such as temperature, fluid levels or other event. The information is then relayed through communication networks to a point of collection and analysis. These devices will need to coexist with the existing device ecosystem.M2M equipment could be a device that is fully self-contained or an embedded device with interfaces to attach to other devices, for example, sensors and health care monitoring tools.

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