WiMAX Migration From Release 1 to Release 2

Migration from

WiMAX Release 1 to WiMAX Release 2

August 2010

Migration from WiMAX Release 1 to WiMAX Release 2

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Table of Contents Migration from WiMAX Release 1 to WiMAX Release 2 ....................................................................... 1

1. Introduction .................................................................................................................................... 3

2. Network Planning Recommendations ............................................................................................ 3

3. Support of Release 1 Terminals .................................................................................................... 4

4. Transition Phases .......................................................................................................................... 4

5. Migration Scenarios ....................................................................................................................... 5

5.1. Migration from Reuse 3 (1x3x3, 3x10 MHz) ........................................................................... 7 5.2. Migration from Reuse 1 (1x3x1, 2x10 MHz overlay) ............................................................... 8

5.3. Migration from Reuse 2 (1x4x2, 2x10 MHz) ........................................................................... 9

6. Performance enhancement during migration from WiMAX Release 1 to WiMAX Release 2 ....... 11

7. References .................................................................................................................................. 12

Appendix A: Frequency Planning Options for 20 MHz Initial Allocation ........................................... 12

Table of Figures Figure 1. Same carrier migration (mixed mode) .................................................................................... 5

Figure 2. Migration to Release 2 with addition of 10 MHz channel ....................................................... 6

Figure 3. Migration from Reuse 3 with addition of 10 MHz channel ...................................................... 7




Figure 7. Migration from Reuse 2 with addition of 10 MHz channel .................................................... 10

Figure 8. Migration from Reuse 2 with addition of 20 MHz channel .................................................... 10

Figure 9. Mixed mode performance of Release 1 and Release 2 ....................................................... 11

Figure 10. (A) 4-Sector – 1x4x2, (B) 3-Sector – 2x3x2, (C) 3-Sector – 1x3x1 .................................... 12


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1. Introduction

The WiMAX Forum is accelerating its development efforts to produce Release 2 equipment based on the

upcoming IEEE Standard 802.16m [1]. The new release will offer significant coverage and capacity

improvements over WiMAX Release 1. The development timeline for Release 2 targets early engineering trials

by mid-2011, with WiMAX Forum certification of equipment by the end of 2011, early commercial availability by

mid-2012, and general commercial availability with rich terminal offerings in 2013. Release 2 service offers a

low-cost solution with seamless migration from Release 1 [1][2]. The Release 2 base station (BS) will provide

full support for Release 1 terminals already deployed using the Release 1 network.

This paper provides basic recommendations for migration from Release 1 to Release 2, assuming that the

migration starts from specific typical WiMAX network deployment scenarios.

2. Network Planning Recommendations

A WiMAX Release 2 system has better cell coverage than one based on Release 1. Therefore, no major

network planning redesign, such as changes to BS location and antenna height, is required. Also, the BS

antenna subsystem and installations, such as cabling, antennas and power amplifiers, will be fully reusable

with minor or no change for Release 2. Core network elements, such as servers and access server network

(ASN) gateways, can be reused with Release 2. The main change will be to swap the channel cards and

perform some software upgrades in certain units. No more than 5% incremental capital expenditure for

migrating from Release 1 to Release 2 is expected.

Fractional frequency reuse (FFR) and segmentation functionality are supported by the Release 2

subchannelization mechanism. Therefore, Release 2 BSs support various sectorization schemes, such as 3-

and 4-sector configurations, while at the same time supporting Reuse 1 operation.

No new coexistence issues will arise between WiMAX networks of the same operator or different operators

(Release 2 – Release 2, or Release 1 – Release 2), as long as reasonable coordination of parameters

between the networks is maintained. As is typically the case for WiMAX Release 1 networks, coordination with

regards to WiMAX frame alignment (including matching downlink-to-uplink ratio), control and data zone


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alignment, and segmentation zone alignment (FFR case) should be sufficient for providing same coexistence

results in the case of Release 2.

3. Support of Release 1 Terminals

A variety of Release 1 terminals have been widely deployed and are operational in more than hundred

WiMAX network deployments worldwide. All Release 1 terminals will operate in the new Release 2 network

without performance degradation since Release 2 networks are backward compatible to Release 1 and all

Release 1 terminals are interoperable in Release 2 networks. Some Release 1 terminals may be capable of

supporting two or more radio access technologies (RATs), such as Wi-Fi, 2G, 3G, EVDO and 3GPP LTE. We

do not expect new inter-RAT issues caused by the migration from Release 1 to Release 2.

The terminals in a Release 2 network can be classified into three categories:

• Cat 1: Supports Release 1 functionality only (but can work in a Release 2 network)

• Cat 2: These devices are Release 2 devices that are backward compatible to Release 1 and can

operate in Release 1 mode.

• Cat 3: Can support only Release 2 functionality

4. Transition Phases

This section addresses transition phases for migration to Release 2. The assumption here is that no

additional spectrum is allocated for the migration. Operators can start transitioning existing Release 1 BSs to

Release 2 BSs one BS at a time. Both Release 1 and Release 2 BSs can coexist in the same network during

the transition process. Release 2 BSs are configured to support a mix of Cat 1, Cat 2 and Cat 3 terminals.

Transition to Release 2 can be done with minimum down time. In most cases, the only change will be

swapping a Release 1 channel card with a Release 2 channel card. All other equipment should be reusable

without any change or with only minor changes. Cat 1 terminals will naturally hand over to the legacy zone of

the BS. Cat 2 terminals would be in Release 1 mode prior to over the transition and will be signaled to move to

Release 2 mode afterwards. Cat 3 terminals can then be introduced when sufficient Release 2 BS coverage is

available.

Cat 1 and Cat 2 terminals can hand over and roam freely across the coexisting Release 1 and Release 2

networks. Cat 3 terminals cannot roam into areas without Release 2 coverage.

Once a segment of the network has fully transitioned to Release 2, Cat 1 terminals should be gradually

phased out. Once all Cat 1 terminals are phased out, the network should be re-tuned to a pure Release 2

operation.


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Figure 1. Same carrier migration (mixed mode)

Figure 1 shows the transition phases in the frame structure from only Release 1 to only Release 2 with an

intermediate phase in which both Release 1 and Release 2 terminals are supported. The resource partitioning

generally targets support for a mixture of terminal categories. Figure 1 illustrates a scenario in which three DL

subframes are allocated to Release 2 operation. During the mixed-mode stage, the BS needs to use the same

Release 1 UL PUSC subchannelization across Release 1 and Release 2 zones in order to guarantee the same

coverage for Release 1 terminals.

5. Migration Scenarios

In many cases, the migration is planned when additional spectrum is available for network capacity

improvement. A simple migration scenario of this type occurs when an additional RF carrier of 10 MHz

becomes available at the time of migration to Release 2 for a legacy Release 1 system based on a 10 MHz

channel used in a Reuse 3 configuration.

Figure 2 illustrates how terminals are served, in this case, by BSs before and after migration. Initially, only 10

MHz Release 1 terminals are operating in the network. As demand for service is increasing, one additional

10MHz channel can be used for migration expansion. In this scenario, the old 10 MHz channel is operating in

Release 1/Release 2 mixed mode and able to serve both Release 1 and Release 2 terminals. The new 10

MHz carrier is dedicated to Release 2 mode of operation only and serving the Release 2 terminals. For more

details on Release 2 support accommodating both legacy terminals and Release 2 terminals please see Figure

1.

Assuming that the two carriers use the same relevant frame configuration parameters, and DL/UL subframe

ratio of the two carriers are fully aligned, smooth transition can be done through utilization of a simple 10+10

Rel. 1

Rel.1/Rel.2

Rel. 2


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MHz multi-carrier operation supported in IEEE 802.16m. According to this scheme, there is no impact on

synchronization and no interference resulting from the new carrier. Moreover, from the viewpoint of legacy

Release 1 terminals, the upgraded system is fully backward compatible with Release 1.

Figure 2. Migration to Release 2 with addition of 10 MHz channel

Migration of a WiMAX Release 1 network, with various spectrum scenarios and reuse configurations, to

Release 2 is supported through IEEE 802.16m advanced multicarrier and mixed mode. WiMAX Release 2

defines various device categories primarily based on performance-based parameters targeting various peak

data rates in difference categories. In addition to performance-based parameters, such as total allocated

bandwidth and number of data streams, other parameters directly related to the operational scenarios, such as

number of aggregating carriers, intra/inter-band and contigious/non-contiguous configurations, are considered

as categorization parameters not directly related to the peak performance.

In the remainder of this section, a number of typical spectrum-related operational scenarios are identified and

migration recommendations related to those are described. More specifically, the following scenarios are

covered:

1. Migration from Reuse 3 (1x3x3, 3x10 MHz), additional 10 and 20 MHz slot 2. Migration from Reuse 1 (1x3x1, 2x10 MHz overlay), additional 10 and 20 MHz slot 3. Migration from Reuse 2 (1x4x2, 2x10 MHz), additional 10 and 20 MHz slot

An intra-band non-contiguous configuration is considered, without loss of generality. Also, additional allocation

sizes of larger than 20 MHz (in the case of Reuse 1 and 3) and larger than 10 MHz (in the case of Reuse 2)

are not covered. Those cases can be covered by simple generalization of other scenarios included here.

Migration scenarios with various Reuse factors without additional spectrum allocations are addressed in the

generic case covered in Section 4.


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5.1. Migration from Reuse 3 (1x3x3, 3x10 MHz)

Figure 3 shows the frame structure associated with migration from Reuse 3 when an additional 10 MHz

channel is available at the time of migration. Here, device categories with 10+10 MHz multi-carrier

aggregation, 10 MHz single-carrier and legacy devices are interoperating in the system.

In the case that multi-carrier 10+10 MHz devices also support 20 MHz 2K FFT channel bandwidth, Release 2

20 MHz channel BSs may serve these devices as well in a roaming scenario.

10 MHz10 MHz

10 MHz

10 MHz

Figure 3. Migration from Reuse 3 with addition of 10 MHz channel

In the case of availability of additional 20 MHz slot, one approach could be to use the 20 MHz spectrum to

overlay two 10 MHz channels with Reuse 1. In this case, Figure 3 can be simply generalized to have F5 as the

second 10 MHz Release 2 channel with Reuse 1 configuration. The advantage of this approach is that the

multi-carrier complexity of Release 2 devices remains as 10+10 MHz.

An alternative to the approach above is to use the additional 20 MHz spectrum for a single 20 MHz Release 2

channel with Reuse 1 configuration. Figure 4 shows the frame structure associated with this migration

scenario. In this case, devices categories with 10+20 MHz multi-carrier aggregation, 10 MHz and 20 MHz

single-carrier and 10 MHz legacy devices are interoperating in the system. In multi-carrier devices, multi-carrier

switching can be used as an alternative to multi-carrier aggregation for lower cost solutions.


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10 MHz10 MHz

10 MHz

20 MHz


5.2. Migration from Reuse 1 (1x3x1, 2x10 MHz overlay)

This section considers the Reuse 1 overlay scenario on 2 of 10 MHz channels. Please refer to Annex A for

more details on frequency planning. Figure 5 shows the frame structure associated with migration from Reuse

1 when an additional 10 MHz channel is available at the time of migration. In here, device categories with

10+10 MHz multi-carrier aggregation, 10 MHz single-carrier and legacy devices are interoperating in the

system.



10 MHz10 MHz

10 MHz



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overlay two 10 MHz channels with Reuse 1. In this case, Figure 5 can be simply generalized to have F5 as

the second 10 MHz Release 2 channel with Reuse 1 configuration. The advantage of this approach is that the




scenario. In this case, devices with 10+10 MHz and 10+20 MHz (10+10+20 MHz not shown in the figure) multi-

carrier aggregation, 10 MHz and 20 MHz single-carrier devices, and 10 MHz legacy devices are interoperating

in the system. In multi-carrier devices, multi-carrier switching can be used as an alternative to multi-carrier

aggregation for lower cost solutions.

10 MHz10 MHz

20 MHz


5.3. Migration from Reuse 2 (1x4x2, 2x10 MHz)

This section considers the Reuse 2 scenario using two 10 MHz channels. Please refer to Annex A for more

details on frequency planning. Figure 7 shows the frame structure associated with migration from Reuse 2

when an additional 10 MHz channel is available at the time of migration. In this case, device with 10+10 MHz

multi-carrier aggregation, 10 MHz single-carrier devices, and legacy devices are interoperating in the system.




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10 MHz10 MHz

10 MHz



overlay two 10 MHz channels with Reuse 1. In this case, Figure 7 can be simply generalized to have F5 as the

second 10 MHz Release 2 channel with Reuse 1 configuration. The advantage of this approach is that the




scenario. In this case, devices with 10+20 MHz multi-carrier aggregation, 10 MHz and 20 MHz single-carrier

devices, and 10 MHz legacy devices are interoperating in the system. In multi-carrier devices, multi-carrier

switching can be used as an alternative to multi-carrier aggregation for lower cost solutions.

10 MHz10 MHz

20 MHz



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6. Performance enhancement during migration from WiMAX Release 1 to WiMAX

Release 2

System capacity depends upon the partitioning among the Release 1 and Release 2 zones. Figure 9 shows

the relative DL average sector throughput, peak sector throughput, and 5%-tile cell edge user throughput

based on simulation results according to the IEEE 802.16m evaluation methodology. As the Release 2 zone

expands, the system performance will increase accordingly. For example, compared to the case of Release 1

only, a 2:3 Release 1:Release 2 mix would bring 20%/40%/60% performance gain in the average/peak/edge

throughputs, respectively. Likewise, pure Release 2 will see a 60%/80%/130% improvement over pure

Release 1.

100%

140%

166%

201%

234%

0%

20%

40%

60%

80%

100%

120%

140%

160%

180%

200%

220%

240%

260%

16e only 3:2 2:3 1:4 16m only

Sector Average

Sector Peak

5% Edge

DL:UL = 5:3, DL MIMO 4x2Sector AverageSector AverageSector AverageSector Average

Sector PeakSector PeakSector PeakSector Peak

5% Edge5% Edge5% Edge5% Edge

100%100%100%100% 140%140%140%140% 166%166%166%166% 201%201%201%201% 234%234%234%234%

Figure 9. Mixed mode performance of Release 1 and Release 2

Table 1 shows the performance improvement when migrating from WiMAX Release 1 to WiMAX Release 2.

For the simulation results in Table 1, the IMT-Advanced UMi test environment is assumed, with 29:18 DL:UL

frame ratio for both Release 1 and Release 2 networks.

Table 1. Performance Improvement

WiMAX Release Bandwidth Sector/site throughput (Mb/s) Site spectral efficiency (b/s/Hz/site)

Release 1, 2x2 10+10 MHz 9.74/58.4 4.73

Release 1, 4x2 10+10 MHz 11.27/67.6 5.48

Release 2, 4x2 20 MHz 37.33/112.0 9.08

Rel.1 Only Rel. 2 Only


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7. References

[1] IEEE P802.16m/D7, DRAFT Amendment to IEEE Standard for Local and metropolitan area networks –

Part 16: Air Interface for Broadband Wireless Access Systems.

[2] IEEE Std 802.16-2009, IEEE Standard for Local and metropolitan area networks – Part 16: Air Interface for

Broadband Wireless Access Systems, 29 May 2009.

[3] DRAFT-T23-001-R010v09-B, WiMAX Forum™ Mobile System Profile, Working Group Approved Revision,

17 May 2010.

Appendix A: Frequency Planning Options for 20 MHz Initial Allocation

Option A (1x4x2): A four-sector deployment with one radio channel per sector. Two sectors use c1 and

the other two sectors use c2. See Figure 10-A.

Option B (2x3x2): A three-sector deployment with one radio channel per sector. One sector uses radio

channel c1 and the other two sectors use c2 (dominant). Cells can interleave c1 and c2 dominance to balance

interference. See Figure 10-B. An alternative configuration can let all three sectors within a cell use radio

channel c1 (or c2). Cells can interleave c1 and c2 to balance inter cell interference.

Option C (1x3x1): A three-sector deployment with two radio channels per sector. Both radio channels (c1

or c2) are used. This is a two-layer scheme. All cells use the uniform channel structure. The initial deployment

could be done with one radio channel per sector and with the second radio channel turned on either selectively

or globally through the network to increase capacity as needed. The two radio channels may be provided by

one or two radio units per sector depending on the transmit power requirements and individual base station

vendor’s offerings. See Figure 10-C.

(A) (B) (C)

Figure 10. (A) 4-Sector – 1x4x2, (B) 3-Sector – 2x3x2, (C) 3-Sector – 1x3x1

WiMAX Migration From Release 1 to Release 2

Documents

lower cost solutions

frequency planning options

radio channel c1

10 20 mhz multi

2x10 mhz overlay

mixed mode performance

10 10 mhz multi

frequency planning