Cost Calculation Distributed Setup

7/29/2019 Cost Calculation Distributed Setup

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What do you expect from a

Cellular service Provider

- LOW SUBSCRIPTION FEE

- HIGH QUALITY CONNECTION


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Outline

Review of the wireless network operation

Limitations of the current network architecture

Description of the new architecture and benefits Backhaul cost reduction: Analysis and results

Increased availability: Analysis and results

Conclusions

Further research topics


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A Simple Wireless NetworkMobile Data Set

PSTN

Packet

Network

MobileVoice Unit

Base TransceiverSystem (BTS)

Base StationController

(BSC)

MobileSwitching

Center (MSC)

Packet Inter-Working Function

Challenge is to keep connection and not loose any data during handoff operation


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The Components

BTS

BTS consists of one or more transceivers placed at a single location.The BTS terminates the radio path on the network side.

BSC

Provides allocation and management of radio resources.

SDU: Selection and distribution unit. Also responsible for handoffcoordination

MSC

Provides and controls mobile access to the PSTN. Interprets the

dialed number, routes and switches call to destination number. Alsomanages mobiles supplementary services. Maintains a register ofvisitors operating within the coverage area of the MSCs connectedBTSs.

PDSN: Packet data service node is basically a packet router.


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MSC PDSN

BSC(SDU)

BSC(SDU)

BSC(SDU)

BTS BTS BTS BTS BTS

- Backhaul cost is by $$$/mile

- 10-100 miles between BTS and BSC

- Voice or data use one DS0 channel at a time

- BTSs are located in the tower

- BSC and MSCs are located

in the central office

Current Wireless Network Architecture

BSC

BTS

24xDs0

in T1

PacketsTDM

channels

TDM

channels


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Soft Handoff between two BTS

Handoffs == ( Hard || Soft )

Handoff: A handoffmechanism is needed to maintain connectivity as devices

move, while minimizing disruptions to ongoing calls. This mechanismshould exhibit low latency, incur little or no data loss, and scale to a large

network.


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SDU and soft handoff

SDU -1

WR-A

SDU-1 -SDU -2

WR-B

-

- 3 to 6 BTSs involved in soft handoff- SDU changeover due to weak signal

from primary BTS

- BTS forwards even corrupted

radio frames to the SDU for selectionSDU -2-

BTS-1

BTS-2

BTS-3


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Problems with the current

architecture Duplicate traffic on the links: Frame selection is done at the BSC (One frame

is generated for each soft handoff leg.) This results in duplicate traffic flow at thebackhaul

No traffic aggregation: Each call is allocated DS0 capacity. Even when there isno activity on the call, the DS0 is reserved. At this rate, currently each BTS cansupport only around 20 calls per sector (normally 3 sectors per BTS). So, no trafficaggregation does not utilize statistical multiplexing (results in inefficient backhaullink provisioning)

If six BTS, then more overhead: Seventy percent (70%) of wirelessoperators expenditure is on RAN. Around 30% expenses are backhaul cost. Only15% of the BTS-BSC traffic is payload and rest is overhead. If six BTS are involved in

the soft handoff then the overhead will be lot higher. Carries dead payload: BTS forwards even error frames to BSC. Because the

selection is done at the BSC. This means we are carrying dead payload to BSC.


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Problems with the current

architecture (cont..) Uneven utilization of links:For data services as well as voice, IP

networks overlay on top of current wireless networks. This is very

inefficient, not cost effective, and very difficult to deploy the new services.

Performance:Less propagation delay. Currently, for some ofthe BTS-BSC configurations, the links run 100 miles, it means

several milliseconds of delay. This creates problem during soft

handoff.

Availability:Less availability due to single point of failure (interms of base stations, base station controllers and links

connecting between them)


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Review

Simple wireless network operation

Different components in the network

Wireless network topology

Mobility and soft handoff

Problems with the existing architecture


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33.1

33.2

33.3

33.4

33.5

33.6

33.7

33.8

33.9

-85.2 -85 -84.8 -84.6 -84.4 -84.2 -84

Typ

USBT

30x

mil

Urban

Rural highway


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2G/3G RAN Network (Traditional)

CO

BTS BTS BTS BTS BTS BTS

CO CO CO

BSC

Interoffice distance (costs per mile) cost + Fixed Cost

Channel

Termination

Cost

ChannelTermination

Cost

MSC


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What configuration is best in

terms of cost and availability Cost Reduction: How and where to place wireless router in the

RAN network with respect to network-level backhaul cost and

availability. For example, existing WR can be part of GSR (high endrouter) ? How close it to BTS

Higher Availability: Distributed IP-RAN for backhaul cost

savings and higher availability

Variables in analysis Different kinds of transport cost structures

Different types of links (T1/T3/Microwave etc.)

Different types of connectivity between BTS and wireless router

Number of carriers supported supported by BTS


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Cost Model Commercial BTS network topology. BTS are connected to BSC using the

chain of Central Offices. Real ILEC cost structure is assumed for the T1 leased lines from urban and

rural areas to the BSC.

20-30 Node network in urban area and 10 BTS in rural areas.

Soft hand factor of 2.0: How many BTS are in soft handoff

1.5 T1 per BTS per carrier BTS Network Regions: I) Dense Urban, ii) Urban iii) Suburban iv) Rural

Cost models

Channel termination costs

Interoffice fixed costs

Per mile costs: Transport cost changes according to distance and the type of

transport (T1/T3/OC3)


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Configurations

Four BTS network configuration are considered:1. Traditional BTS-BSC network (Config-1, fully star, call it

Traditional)

2. One Wireless Router supporting multiple BTSs (10-30). Forexample, existing WR can be part of GSR (high end router) ? How

close it to BTS (Config-2, call it star)

3. Meshed Wireless Routers (Config-3, one wireless router per BTS,

full mesh within the central office region. Call this WR)

4. Meshed Wireless Routers (WR) and each WR connected tomultiple Gateway Routers for higher availability (Config-4, with

connection to all the nearby high end routers. Call this WR-HA)


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2G/3G RAN Network (Traditional)

CO


CO CO CO

BSC

Interoffice distance (costs per mile) cost + Fixed Cost

ChannelTermination

Cost

ChannelTermination

Cost

MSC

- Around 150 BTS per BSC


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WR supports multiple BTS (10-20). Selection and distribution is done in the WR. WR collocated with CO

WR supporting multiple BTSs (Star Topology)

WR

WR-BTS

links


WR

WR-BTS

links


CO CO


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Solution: Distributed Control

GRGateway Router

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

WR

GRGateway Router

Radio frames

Embedded in

IP packets

Each packet

Contains several

radio frames.

Wireless Router is an IP router

with RF termination. Functions

include BTS, SDU, power

control, and handoff control

Gateway Router is a IP routerconnected to the internet core


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WR-WR

Links

WR-WR

Links

WR

WR/BTSWR/BTS

WR/BTSWR/BTS

GRGateway Router

WR

WR/BTSWR/BTS

WR/BTSWR/BTS

GRGateway Router

GR-GR links

WR-GR links

Solution (cont.)

- Radio frame routing

using IP routing

- Radio neighbors exchange

resource info. using IP

routing protocols

- Mobility is handled through

IP signaling protocols

- Radio resource management

is handled by IP traffic

management

- WR assumes SDU function

Transit traffic management is

handled by IP routing, QoS


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Solution (cont.)

Distributed SDU. Distributed bearer and control Radio Routing Protocol: IP routing merged with Radio frame

routing for soft handoff and mobility. Wireless extensions of OSPFwith radio neighbors.

Radio Discovery Protocol: Discovering Radio Neighbors Radio Resource Management: IP traffic management

merged/enhanced with Radio Traffic Management. Radio PowerControl integrated and aligned with IP QoS

RSVP extensions for Radio: IP resource managementmerged/enhanced with Radio Resource Management. For example,

Radio Resource Management and soft hand off signaled withRSVP.

IP transport in Radio Access Network

Disruptive Technology


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Benefits

Cost Reduction: Efficient use of backhaul links and

aggregation. Only 15% of the BTS-BSC traffic is payload

and rest is overhead. Around 30% expenses are backhaul

cost.Objective is to reduce the backhaul traffic and smallnumber of high speed backhaul links.

Scalability: Separation of call processing and bearer paths

Distributed SDU and Distributed Control

Ability to provide coverage and capacity during peak hours

Redundancy and Availability: Due to meshed architecture,

network is robust and works around the failures.


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Benefits (continued)

Marriage of IP and wireless protocols: Seamless operation of

IP-Network-Layer with Radio Control.

Reuse already deployed routers in the Central Offices.

New wireless services:Automatic Reconfiguration of Radio AccessNetwork. Expand cell attributes to provide more capacity

Performance:Less propagation delay. Currently, for some of theBTS-BSC configurations, the links run 100 miles, it means several

milliseconds of delay. This creates problem during soft handoff. Due to

short lengths between base stations, the delay will be negligible.


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WR collocated with BTS (WR)

WR-GRlinks

WR

WR/BTSWR/BTS

WR/BTSWR/BTS

Central Office

WR-WR

Links

GR

Gateway Router

WR-GRlinks

WR

WR/BTSWR/BTS

WR/BTSWR/BTS

Central Office

WR-WR

Links

GR

Gateway Router

* WR-GR link (primarily) used for backhauling selected traffic to the destination

* WR-WR link (primarily) is used for selection and distribution traffic between

two wireless routers.

* GR-GR links are links between two IP routers. These routers do not distinguish between wireless and wireline traffic

GR-GR links

WR ll t d ith BTS ith HA (WR HA)


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WR collocated with BTS with HA (WR-HA)

WR-GR

links

WR

WR/BTSWR/BTS

WR/BTSWR/BTS

Central Office

WR-WR

Links

GR

Gateway Router

WR

WR/BTSWR/BTS

WR/BTSWR/BTS

Central Office

WR-WR

Links

GR

Gateway Router

GR is collocated in the the closest CO

Connectivity to two (atleast) GRs is established for higher availability. The second GR is collocated in the

neighboring Central office.


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Traffic Models

scheduler

Overhead /container

Overhead/ stream

Overhead/ stream

voicestream

voicestream

multiplexer

packetizerDt

multiplexer

packetizerDt

Overhead/ stream

Overhead/ stream

datastream

datastream

Segment. Segment.

Traffic Mix

100% voice + 0% data

100% data, 14.4K, 64K and 144Kbps

80 % voice + 20% data, 14.4K, 64K and 144Kbps

20 % voice + 80% data, 14.4K, 64K and 144Kbps


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Cost ComparisonsUrban (30 node network)

0100000

200000

300000

400000500000

600000

700000

800000

WR(one per BTS)

WR with HATraditional

Star (10 BTS per WR)

No. of Carriers (increased bandwidth at BTS, 1carrier requires ~~2 Mpbs)

$$$$$


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Cost ComparisonRural (around 10 nodes)

0

100000

200000

300000

400000

500000

600000

1 2 3 4 5 6 7 8 9 10 11 12

WR

WRHA

Trad

Star

No. of Carriers (increased bandwidth at BTS, 1carrier requires ~~2 Mpbs)

$$$$


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Why less cost ??

Backhaul cost reduced with WR mesh architecture.Customer saves $$$$ (per mile backhaul cost)

Why is the backhaul much less with WR? What is

new with WR? Frame Selection is done at the WR. No duplicate traffic

after the selection is done

The aggregation of voice and data traffic from multiple

WRs enables better Statistical multiplexing and reduces thebackhaul requirement. This also enables customer to use lesscostly T3 and saves them more $$$$

Flexible and more reliable traffic routing.


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Review and Conclusions

Statistical multiplexing and compression techniques are not accounted

in the results described. If counted, more savings are realized

Cost savings for one carrier are not much but substantial for multiple

carriers. Star at the near-by-CO with a high speed (e.g., DS3/OC3) uplink is the

optimum but without higher availability.

Mesh is ideal for higher availability and cost savings

All the WR cases win over traditional deployment

Ongoing work: Different kinds of transport cost structures anddifferent types of links (T1/T3/Microwave etc.)


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Service Availability

CO CO CO CO

BSC

MSCBTS BTSBTS BTS BTS

BTSWR

WR

WR

WR

WR

WR

WR

WR

WR

- Rerouting around failed links/nodes

- Rerouting around congested links/nodes- Wireless router is also IP router hence no

need to deploy full mesh

- If BTS fails, neighboring resources can be

used to complete the calls.

-Single point of failure at BTS- Single point of failure at BSC

- No rerouting around congested nodes

possible.


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Availability Model (example)

Tower

WR

WR

WR

WR

WR

WR

WR

WR

GR

GR

Backplane

Line Card

Line card

Control

Processor

Control

Processor

SW

SW

Calculate MTBF and MTTR of all the components in each element


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Annual Down Time Comparison

Link Avail .99 .999 .9999 .99999

Traditional(Hours)

174 17.77 2.01 0.438

WR-HA

(Minutes)

5.25 5.25 5.25 5.25

BTS Availability: 0.99999

GR Availability: 0.99999

Link availability is varied from 0.99 to 0.99999 and downtime is computedFor traditional and WR-HA network topologies.


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Annual Down Time Comparison

Link Avail .99 .999 .9999 .99999

Traditional

(Hours)

174 17.77 2.01 0.438

WR-HA

(Minutes)

5.85 5.78 5.78 5.78

Assumptions:

BTS Availability: 0.99999

GR Availability: 0.99

Link availability is varied from 0.99 to 0.99999 and downtime is computed

For traditional (2G/3G) and WR-HA network topologies.


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RESULTS

In conventional case, when a link fails, the call level reliability is low

because the call is not redirected without dropping. However, in mesh

architecture, the call can still be maintained and the rerouting takes

place at the frame/packet level.

Though GRs availability is only 0.99, the overall service downtime is

not impacted due to the fact that there are multiple paths from BTS to

another GR.


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Review and Conclusions

Distributed RAN architecture saves backhaul cost (less than half of the

cost of existing architecture )

Distributed RAN architecture supports 99.999% service-level

availability compared to conventional network. In fact, full mesh is notrequired for realizing the 99.999% availability. Even partial mesh can

achieve this level of availability

Distributed architecture increases the complexity of control and

requires working prototype for understanding the new protocols.

Disruptive technology: Required new protocols design and approvalfrom vendor and hence may take long time to get to the field (this is

weakness in this architecture).

Documents

Cost Calculation Distributed Setup