This white paper discusses interference scenarios that can occur between WiMAX and LTE systems deployed in adjacent spectrum blocks. It provides recommendations for mitigating interference between unsynchronized WiMAX and LTE systems, including the need for large guard bands. The paper also presents a specific solution to synchronize and align the downlink/uplink splits of WiMAX and LTE-TDD systems, which could eliminate the need for guard bands and other costly interference mitigation measures. However, this solution may not always be possible due to the impact on operators' business plans and the services they aim to provide.
Qualcomm is elevating its role as a market leader by bringing breakthrough concepts to LTE’s evolution. We believe that the next significant performance leap will come from heterogeneous networks, or HetNets, which bring the network closer to the user through low-power nodes such as pico and femto-cells. LTE Advanced uses adaptive interference management techniques to further improve the capacity and coverage of these HetNets. There by, ensuring fairness among users and an enhanced mobile experience, especially for those users at the cell edge. LTE Advanced also introduces multicarrier to leverage ultra wide bandwidths up to 100 MHz, supporting very high data rates.
Main Differences between LTE & LTE-AdvancedSabir Hussain
LTE stands for Long Term Evolution.
In Nov. 2004, 3GPP began a project to define the long-term evolution (LTE) of Universal Mobile Telecommunications System (UMTS) cellular technology.
LTE systems have:
Higher performance
Backwards compatible
Wide application
Data Rate:
Instantaneous downlink peak data rate of 100Mbit/s in a 20MHz downlink spectrum (i.e. 5 bit/s/Hz)
Instantaneous uplink peak data rate of 50Mbit/s in a 20MHz uplink spectrum (i.e. 2.5 bit/s/Hz)
Cell range:
5 km - optimal size
30km sizes with reasonable performance
up to 100 km cell sizes supported with acceptable performance
Cell capacity:
up to 200 active users per cell(5 MHz) (i.e., 200 active data clients)
Mobility
Optimized for low mobility(0-15km/h) but supports high speed
Latency (delay)
user plane < 5ms
control plane < 50 ms
Improved broadcasting
IP-optimized
Scalable bandwidth of 20MHz, 15MHz, 10MHz, 5MHz and <5MHz
Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, when there is no coverage, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS)
LTE Advanced is a mobile communication 4G standard approved by International Telecommunications Union (ITU) in Jan 2012.
LTE-Advanced (LTE-A) is an emerging and, as the name suggests, a more advanced set of standards and technologies that will be able to deliver bigger and speedier wireless-data payloads.
The most important thing to know is that LTE-A promises to deliver true 4G speeds, unlike current LTE networks. You can expect the real-world speed of LTE-A to be two to three times faster than today’s LTE.
To be considered true 4G (also known as “IMT-Advanced”), a mobile network must fulfill a number of benchmarks, including offering a peak data rate of at least 100 megabits per second (Mb/s) when a user moves through the network at high speeds, such as in a car or train, and 1 gigabit per second (Gb/s) when the user is in a fixed position.
The highest possible rates are never achieved in real world conditions. Actual rates will be variable, but we can expect LTE-A to be at least five times as fast as most LTE networks today, and that’s great news for video streaming.
LTE Advanced is supposed to provide higher capacity, an enhanced user experience, and greater fairness in terms of resource allocation.
It does this by combining a bunch of technologies, many of which have been around for some years, so we’re not really talking about the implementation of an entirely new system here.
Qualcomm is elevating its role as a market leader by bringing breakthrough concepts to LTE’s evolution. We believe that the next significant performance leap will come from heterogeneous networks, or HetNets, which bring the network closer to the user through low-power nodes such as pico and femto-cells. LTE Advanced uses adaptive interference management techniques to further improve the capacity and coverage of these HetNets. There by, ensuring fairness among users and an enhanced mobile experience, especially for those users at the cell edge. LTE Advanced also introduces multicarrier to leverage ultra wide bandwidths up to 100 MHz, supporting very high data rates.
Main Differences between LTE & LTE-AdvancedSabir Hussain
LTE stands for Long Term Evolution.
In Nov. 2004, 3GPP began a project to define the long-term evolution (LTE) of Universal Mobile Telecommunications System (UMTS) cellular technology.
LTE systems have:
Higher performance
Backwards compatible
Wide application
Data Rate:
Instantaneous downlink peak data rate of 100Mbit/s in a 20MHz downlink spectrum (i.e. 5 bit/s/Hz)
Instantaneous uplink peak data rate of 50Mbit/s in a 20MHz uplink spectrum (i.e. 2.5 bit/s/Hz)
Cell range:
5 km - optimal size
30km sizes with reasonable performance
up to 100 km cell sizes supported with acceptable performance
Cell capacity:
up to 200 active users per cell(5 MHz) (i.e., 200 active data clients)
Mobility
Optimized for low mobility(0-15km/h) but supports high speed
Latency (delay)
user plane < 5ms
control plane < 50 ms
Improved broadcasting
IP-optimized
Scalable bandwidth of 20MHz, 15MHz, 10MHz, 5MHz and <5MHz
Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, when there is no coverage, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS)
LTE Advanced is a mobile communication 4G standard approved by International Telecommunications Union (ITU) in Jan 2012.
LTE-Advanced (LTE-A) is an emerging and, as the name suggests, a more advanced set of standards and technologies that will be able to deliver bigger and speedier wireless-data payloads.
The most important thing to know is that LTE-A promises to deliver true 4G speeds, unlike current LTE networks. You can expect the real-world speed of LTE-A to be two to three times faster than today’s LTE.
To be considered true 4G (also known as “IMT-Advanced”), a mobile network must fulfill a number of benchmarks, including offering a peak data rate of at least 100 megabits per second (Mb/s) when a user moves through the network at high speeds, such as in a car or train, and 1 gigabit per second (Gb/s) when the user is in a fixed position.
The highest possible rates are never achieved in real world conditions. Actual rates will be variable, but we can expect LTE-A to be at least five times as fast as most LTE networks today, and that’s great news for video streaming.
LTE Advanced is supposed to provide higher capacity, an enhanced user experience, and greater fairness in terms of resource allocation.
It does this by combining a bunch of technologies, many of which have been around for some years, so we’re not really talking about the implementation of an entirely new system here.
LTE & Wi-Fi: Options for Uniting Them for a Better User ExperienceAricent
Most national governments consider the radio spectrum a valuable national resource and heavily regulate its commercial use. Governments typically auction off licenses for the right to transmit over a portion of the spectrum, which can be very expensive. The traditional business model for cellular
carriers is based on access to this licensed business has coalesced worldwide around a single 4th generation (4G) radio technology standard called Long Term Evolution, commonly referred to as LTE.
This seminar will provide the basics of this fascinating technology. After attending this seminar you will understand OFDM-principles,
including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO) is a fundamental
part of LTE and its impact on the design of device and network architecture will be explained. Further LTE-related physical layer
aspects such as channel structure and cell search will be presented with an overview of the LTE protocol structure.
The second part of the seminar provides an overview of the evolution in LTE towards 3GPP specification Release 9 and 10. This
includes features and methods for location based services like GNSS support or time delay measurements and the concept of
multimedia broadcast. Finally, we’ll introduce the main features of LTE-Advanced (3GPP Release-10) including carrier aggregation for
a larger bandwidth and backbone network aspects like self-organizing networks and relaying concepts.
Industry-supported field trials are already demonstrating the viability of many of the
technical concepts in LTE-Advanced. The approach is to increase data rates for all
users, bring more out of small cells, dynamically adapt to network load and use of
more carriers for more speeds. Also there will be unprecedented ecosystem of handset-manufacturer, software-developers and chip-designers that will support this intelligent
network.
In this presentation we will briefly discuss principle technologies that are being adopted
in LTE-Advanced. We will understand the basics of the technologies that are under
developmental stages and look if we can contribute to their future enhancements.
LTE & Wi-Fi: Options for Uniting Them for a Better User ExperienceAricent
Most national governments consider the radio spectrum a valuable national resource and heavily regulate its commercial use. Governments typically auction off licenses for the right to transmit over a portion of the spectrum, which can be very expensive. The traditional business model for cellular
carriers is based on access to this licensed business has coalesced worldwide around a single 4th generation (4G) radio technology standard called Long Term Evolution, commonly referred to as LTE.
This seminar will provide the basics of this fascinating technology. After attending this seminar you will understand OFDM-principles,
including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO) is a fundamental
part of LTE and its impact on the design of device and network architecture will be explained. Further LTE-related physical layer
aspects such as channel structure and cell search will be presented with an overview of the LTE protocol structure.
The second part of the seminar provides an overview of the evolution in LTE towards 3GPP specification Release 9 and 10. This
includes features and methods for location based services like GNSS support or time delay measurements and the concept of
multimedia broadcast. Finally, we’ll introduce the main features of LTE-Advanced (3GPP Release-10) including carrier aggregation for
a larger bandwidth and backbone network aspects like self-organizing networks and relaying concepts.
Industry-supported field trials are already demonstrating the viability of many of the
technical concepts in LTE-Advanced. The approach is to increase data rates for all
users, bring more out of small cells, dynamically adapt to network load and use of
more carriers for more speeds. Also there will be unprecedented ecosystem of handset-manufacturer, software-developers and chip-designers that will support this intelligent
network.
In this presentation we will briefly discuss principle technologies that are being adopted
in LTE-Advanced. We will understand the basics of the technologies that are under
developmental stages and look if we can contribute to their future enhancements.
Og 102 site survey and layout of bts issue1.5Ketut Widya
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Billions of connected devices and things. Billions of people. 5G will provide connectivity for all of these things and people as well as businesses and industry, bringing benefit to society. Operating machinery in hazardous environments from a remote control will be enabled through near-zero latency communication links that enable real-time video. Billions of video-enabled devices will be able to share bandwidth-hungry content. These are just a few applications that illustrate what 5G will be designed for.
In this paper, we discussed about LTE system throughput calculation for both TDD and FDD system.
3GPP LTE technology support both TDD and FDD multiplexing. The paper describes all the factors which affect the throughput like Bandwidth, Modulation, UE category and mulplexing. It also describes how we get throughput 300Mbps in DL and 75Mbps in UL and what are assumptions taken to calculate the same.
Paper describes the steps and formulae to calculate the throughput for FDD system for TDD Config 1 and Config 2.
The throughput calculations shown in this paper is theoretical and limited by the assumptions taken to calculate for calculations
Heterogeneous LTE Networks and Inter-Cell Interference Coordination - Dec 201...Eiko Seidel
Initial deployments of LTE networks are based on so-called homogeneous networks consisting of base stations providing basic coverage, called macro base stations. The concept of heterogeneous networks has recently attracted considerable attention to optimize performance particularly for unequal user or traffic distribution. Here, the layer of planned high-power macro eNBs is overlaid with layers of lower-power pico or femto eNBs that are deployed in a less well planed or even entirely uncoordinated manner. Such deployments can achieve significantly improved overall capacity and cell-edge performance and are often seen as the second phase in LTE network deployment.
This paper discusses the concept of heterogeneous networks as compared to homogeneous networks. It demonstrates the need for inter-cell interference coordination (ICIC) and outlines some ICIC methods that are feasible with release 8 /9 of the LTE standard. System-level simulation results illustrate the benefits of the various features discussed in the following.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
5G NR is a contradictory complex, and it is difficult to have both capacity and coverage. 5G expands the system capacity by expanding the bandwidth of the spectrum. The frequency range extends from below 3GHz in the 4G era to the millimeter wave band, and the single carrier bandwidth is increased from 20MHz to more than 100MHz. But the higher the frequency band, the smaller the coverage of the base station, and the operator has to build more base stations.
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The purpose of 5G flexible duplexing is to allow the most flexible use of an operator's spectrum for time-frequency resources in a single framework. 5G Flexible duplexing should inherently support both paired and unpaired spectrum and be forward compatible with full-duplex 5G.
Evaluation of Percentage Capacity Loss on LTE Network Caused by Intermodulati...Onyebuchi nosiri
Abstract- The paper evaluates the effects of third order Intermodulation Distortion (IMD3) on the Long Term Evolution (LTE) receiver due to coexistence between LTE and GSM networks. Amongst the various existing IMD orders which include first order, second order, third order, fifth order and seventh order. Third order is known to have the greatest distortion effects on a receiver due to its strength and its proximity to the frequency band of interest. It occurs as a result of the non-linear behavior of components or circuit at both the transmitter and receiver ends of wireless communication networks. IMD has potential negative effects on a victim receiver which majorly leads to increase in noise floor level and system capacity degradation. Deterministic approach was implemented in the work assuming worst case scenario. MATLAB software simulation was deployed to evaluate the capacity loss at the receiver end relative to a range of distances apart. Results obtained showed severe uplink capacity degradation when VISAFONE LTE network was interfered by INTERCELLULAR LTE downlink and ETISALAT GSM uplink. Various distances ranging from 500m to 3000m were varied between the ETISALAT GSM network and the VISAFONE LTE network. The results obtained showed that at 500 meters, the percentage capacity degradation was as high as 80. The least percentage capacity loss was obtained as 5.97 at 3000 meters.
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Nokia td lte-and_wimax_coexistence_and_migration
1. Nokia Networks white paper
TD-LTE and WiMAX coexistence and migration
TD-LTE and WiMAX
coexistence and migration
Nokia Networks
2. Page 2 networks.nokia.com
Contents
Introduction 3
Interference scenarios in WiMAX-LTE coexistence 4
Recommendations for WiMAX/LTE-FDD and
Unsynchronized/non aligned DL/UL splits
WiMAX/LTE-TDD coexistence
6
Specific solution for WiMAX/LTE-TDD coexistence:
Synchronizing and aligning DL/UL splits
8
Summary 10
Abbreviations 11
Appendix A 11
Innovation is happening right now at Nokia
Many of the innovations from previous years described in this document are still relevant today and have been developed to support the
optimization of mobile broadband networks and services.
Looking ahead, Nokia will continue to focus on innovation and we will be updating this document to reflect the latest developments.
3. Page 3 networks.nokia.com
Introduction
Nokia Networks strong experience and expertise in TD-LTE, LTE FDD
and WiMAX provides the operator with confidence that they are getting
an efficient, highquality and reliable network.
One important question on a lot of operator minds is: How to deploy
TD-LTE next to WiMAX and then migrate WiMAX to TD-LTE?
The answer to this question is as varied as the many different operator
business models. The one constant, however, is that interference
mitigation can be very costly and involve a complex set of issues. If
not properly addressed, interference can wreak havoc on a network
resulting in smaller bits of useable spectrum, less capacity to handle
heavy data usage and subscriber growth, and ultimately dissatisfied
customers. In this increasingly competitive marketplace where the cost
of acquiring spectrum is a major debt burden that operators may carry
for years, it is crucial to resolve interference issues quickly and optimize
network performance right from the start.
In this white paper, we discuss the interference scenarios between
WiMAX system and LTE system in adjacent spectrum blocks,
recommendations and specific solution for WiMAX/TD-LTE coexistence.
4. Page 4 networks.nokia.com
Interference scenarios in WiMAX-LTE
coexistence
When WiMAX and LTE-FDD are deployed in adjacent spectrum blocks,
several interference scenarios could occur between the WiMAX and
LTE-FDD system, as shown in the Figure 1.
LTE-FDD UL WiMAX WiMAX LTE-FDD DL
LTE-FDD UE WiMAX BTS WiMAX BTS LTE-FDD UE
LTE-FDD UE WiMAX UE WiMAX UE LTE-FDD UE
WiMAX BTS LTE-FDD BTS LTE-FDD BTS WiMAX BTS
WiMAX UE LTE-FDD BTS LTE-FDD BTS WiMAX UE
Fig. 1. Potential interference scenarios for WiMAX and LTE-FDD coexistence
LTE-TDD WiMAX
LTE-TDD BTS WiMAX BTS
LTE-TDD UE WiMAX UE
LTE-TDD UE WiMAX BTS
LTE-TDD BTS WiMAX UE
WiMAX BTS LTE-TDD BTS
WiMAX UE LTE-TDD UE
WiMAX UE LTE-TDD BTS
WiMAX BTS LTE-TDD UE
Fig. 2. Potential interference
scenarios for WiMAX and
LTE-TDD coexistence
If WiMAX and LTE-TDD are deployed in adjacent spectrum blocks, a
similar set of interference scenarios could occur. Please see Figure 2.
However, in the WiMAX/LTE-TDD case, the severity of the interference
will depend on overlap of the WiMAX DL/UL frame with the LTE-TDD DL/
UL frame as shown in the Figure 3.
Among these different interference scenarios, it is noted that the BTS
-to-BTS and UE-to-UE interference are typically the most problematic
interference scenarios. This is mainly because the BTS-to-BTS
interference could impact the performance of the whole sector.
BTS-to-BTS interference can be mitigated to some extent by using
filters with sharp roll off characteristics.
For the UE-to-UE worst case interference scenario, the interfering UE
could be transmitting at a high power in close proximity to the victim UE
which is itself receiving a poor desired signal from its own BTS – causing
very unpleasant user experience. Such scenarios could occur in areas
where users aggregate such as in a conference room, an airport, or a
stadium.
For UEs the transition bands of filters tend to be much wider
which requires large guard bands to protect the worst case UE-to-
UE interference scenarios mentioned above. However, UE-to-UE
interference is probabilistic in nature and depends on many factors
including transmit power, and distance between UEs. So, protecting
against worst case UE-to-UE interference scenarios could result in some
aggressive guard band requirements as discussed in the next section.
The BTS-to-UE and UE-to-BTS interference are typically less severe and
could be mitigated by co-location the BTSs of the two systems.
5. Page 5 networks.nokia.com
For detailed UE-to-UE interference analysis, please refer to Appendix A.
ULDL
LTE-TDDULDL
ULDL
DLUL
DL
DL
UL
UL
WiMAX
WiMAX
LTE-TDD
WiMAX
LTE-TDD
No UE UE & BS BS
Interference for both operators
UE UE & BS BS
Interference all the time for both operators when UEs & BSs
are under conditions to cause interference
• UE UE interference portion of the time for operator A
when UEs are under conditions to cause interference
• BS BS interference portion of the time for operator B
when BSs are under conditions to cause interference
• UE BS and BS UE interference
Complete synch
Complete unsynch
Partial synch
Fig. 3. WiMAX/LTE-TDD coexistence as a function of DL/UL overlaps of the 2 systems
6. Page 6 networks.nokia.com
Recommendations for WiMAX/LTE-FDD
and unsynchronized/non aligned DL/UL
splits WiMAX/LTE-TDD coexistence
Our recommendations for WiMAX/LTE-FDD and unsynchronized/non
aligned DL/UL splits WiMAX/ LTE-TDD systems are as follows:
BTS to UE and UE to BTS interference
• Usually analyzed by Monte Carlo simulation and expected to be less
critical than BTS-to-BTS and UE-to-UE based interference.
• Could be mitigated by colocation of the BTSs of the two systems.
BTS to BTS interference
• Deterministic desense analysis is usually used for BTS-to-BTS
interference analysis.
• Very selective filter providing stringent transmit out-of-band
emission of -45dBm/1MHz EIRP allows protection for co-located BTS
deployments with 50 dB antenna port to antenna port isolation or
non co-located BTSs with 100 m separation distance. If coexistence
under more severe conditions is expected, then other solutions
would need to be explored.
• Receive blocking could be an issue if based on current 3GPP blocking
specification. Actual product performance could be better. Very
selective filter would be needed on Receive. In the case of TDD, the
transmit and receive filters are the same.
• Potentially at least 5MHz guard band is needed to meet the
stringent Transmit emission and receiver blocking requirements for
coexistence.
• Operator coordination/agreement and good site planning
encouraged.
7. Page 7 networks.nokia.com
UE to UE interference
• Is a probability function depending on:
• Channel bandwidth and band plan
• Geographical separation between UEs
• UE transmit power
• Maximum transmit power is worst case
• Average or 95% CDF taking into account power control might be
more realistic
• UE receive characteristics
• Interference criteria (stringent vs. less stringent)
• 1 dB increase in noise floor as strict criterion
• More relaxed 3dB increase in noise floor can also be used
• Could happen when the interfering UE is very close to the victim
UE in a high user density area where the physical separation is very
limited to provide enough isolation.
• Worst case protection with the interfering UE transmitting at
maximum power and within 1m of victim UE which is itself receiving
a poor signal would require 10 MHz guard band if we rely only
on the UE filter to mitigate the interference. This corresponds
to the transition band of the UE filter which takes into account
temperature and other variations.
• If less stringent interference criteria are allowed, i.e., operators
are willing to accept higher level of interference then 5MHz of
guard band could be needed (similar to what is needed to mitigate
interference between BTSs) based on a 3dB desense criterion, 5 m
separation and lower transmit power due to power control.
• Network control solution to further reduce out-of-band emission
for coexistence with at least 5MHz guard band is also possible. This
measure takes advantage of the fact that an LTE UE out-of-band
emission is a function of the power, number and location of the
resource blocks with the channel.
• Schedule high power users away from channel border
• Restrict the transmit power, subcarrier allocation for users
assigned in the region close to the channel border
• Similar solution was adopted for 3GPP Band 13 to solve LTE UE
to Narrow Band Public Safety Portable interference in US 700
MHz band
• PUCCH solutions needed
• Requires action in 3GPP
• WiMAX solutions to be explored
• Explore other potential advanced interference cancelation schemes.
• Explore alternate wireless topologies solutions (e.g., indoor
pico cells).
8. Page 8 networks.nokia.com
Specific solution for WiMAX/TD-LTE
coexistence: Synchronizing and aligning
DL/UL splits
The previous section addresses the case where WiMAX and TD-LTE
are not synchronized and have different DL/UL splits. In that case,
at least 5MHz of guard bands along with selective filters on BTSs,
smart scheduling, restriction on resource blocks and site engineering
measures are potentially needed to mitigate the critical BTS-to-BTS
and UE-to-UE interference. Therefore, to reduce or even eliminate
the need for these costly measures, one potential solution would
consist of:
• frame synchronization and aligning DL/UL splits to eliminate the
BTS-to-BTS and UE-to-UE problem (e.g., via GPS).
• co-location of WiMAX and TD-LTE BTSs to avoid the classic BTS/UE
near-far problems.
However, this solution implies the use of specific DL/UL splits in the
WiMAX and TD-LTE systems which are not always possible because of
the impact to the business plans of the operators and the services
they want to provide (e.g., a broadcast system would be mostly
downlink and hard to align with a system that has a 50:50 DL/UL
splits for example). If it is the same operator controlling both systems
as in the case of a WiMAX to TD-LTE migration scenario, then it would
be easier to synchronize and align the DL/ UL splits of both systems.
The operators need to evaluate if such measures are reasonable and
outweigh the impact of BTS to BTS and UE to UE interference on their
system performance and the additional costs needed to mitigate the
interference.
Configuration Switch-point periodicity Subframe number
O 5 ms D S U U U D S U U U
1 5 ms D S U U D D S U U D
2 5 ms D S U D D D S U D D
3 10 ms D S U U U D D D D D
4 10 ms D S U U D D D D D D
5 10 ms D S U D D D D D D D
6 5 ms D S U U U D S U U D
0 1 2 3 4 5 6 7 8 9
Fig. 4. TD-LTE subframe configurations
9. Page 9 networks.nokia.com
In order to time align a TD-LTE with WiMAX, the TD-LTE system must
use a similar 5 ms switching period as well as a similar downlink and
uplink transmission period.
Referring to figure 4, TD-LTE supports four configurations with a
5 ms switching period, configuration 0, 1, 2 and 6. Of these, only the
first three have an identical downlink/uplink transmission sequences
in the first 5 and second 5 subframes of the 10 ms TD-LTE frame.
The identical transmis-sions are necessary to make the 10 ms TD-LTE
frame compatible with the 5 ms WiMAX frame.
Synchronizing with a WiMAX 29:18 frame configuration
TD-LTE frame configuration 1 has similar transmission periods to the
typical WiMAX DL: UL ratio of 29:18. For illustration purposes, special
subframe format 4 is used to provide an approximate match to the
WiMAX 29:18 frame with only a 2% overlap between BTS and MS
transmission periods. Figure 5 illustrates the compatible TD-LTE and
WiMAX frame structures. Note that the TD-LTE radio frame starts 1 ms
later than the WiMAX frame.
Note that while Special subframe format 4 is used for illustration
purposes, other Special subframe format configurations like 7 or 5 can
also be allowed to align with WiMAX frame.
Two options may be employed to eliminate the remaining overlap in
downlink transmission period of WiMAX and the uplink transmission
period of TD-LTE:
• WiMAX downlink symbols may be dropped to eliminate the overlap.
If the WiMAX downlink period is reduced by 2 symbols there will be
no overlap between the WiMAX downlink and TD-LTE uplink. WiMAX
would then be 27 DL:18 UL instead of 29 DL:18 UL. This results
in a maximum throughput reduction of 7% (=2/29) to the WiMAX
downlink with no loss to the TD-LTE system.
• TD-LTE UpPTS may be dropped to eliminate the overlap. This results
in no degradation to the downlink or uplink data throughput to
WiMAX. Dropping of the UpPTS reduces the TD-LTE SRS and PRACH
resources and hence there is minimal impact to the throughput.
29 symbolsWiMAX
TD-LTE
SUBFRAME 1
SUBFRAME 9
1ms
5ms
Uplink DwPTS GP UpPTS Downlink
SUBFRAME 0
18 symbols
SUBRFRAME 2 SUBRFRAME 3
Fig. 5. Compatibility of TD-LTE and 29:18 WiMAX subframes
10. Page 10 networks.nokia.com
Synchronizing with a WiMAX 35:12 frame configuration
TD-LTE frame configuration 2 has downlink/uplink transmission
periods that are similar to the 35:12 WiMAX frame structure. LTE
special subframe format configurations 5 and 6 are both fully
compatible with the 35:12 WiMAX frame structure, and support a cell
radius of at least 15km (assuming WiMAX and TD-LTE co-location). Due
to significant overlap between LTE downlink transmission and WiMAX
uplink when using special subframe formats 4 or 7, these special
subframe format configurations are not compatible with a 35:12
WiMAX frame. Also note that the TD-LTE radio frame starts 2 ms later
than the WiMAX frame for this TDD configuration.
35 symbolsWiMAX
TD-LTE SUBFRAME 1SUBFRAME 8
1ms
5ms
Uplink DwPTS GP UpPTS Downlink
SUBFRAME 9 SUBFRAME 0
12 symbols
SUBRFRAME 2
Fig. 6. Compatibility of TD-LTE and 35:12 WiMAX subframes
Summary
LTE and WiMAX coexistence requires study of various interference
scenarios. Nokia Networks offers a high level set of recommendations
and solutions. These recommendations can help operators increase
capacity, reduce churn and ultimately realize higher margins from
delighted customers anxious to take advantage of the exciting new
benefits of 4G.
At Nokia Networks, we offer the technology, the knowledge and the
experience to help operator and spectrum owners take immediate
advantage of the escalating demand for mobile broadband data
service and applications.
If you have questions about the coexistence of WiMAX and LTE talk
with your Nokia Networks representative.
11. Page 11 networks.nokia.com
Abbreviations
BTS Base station
CDF Cumulative Distribution Function
DL Downlink
DwPTS Downlink Pilot Time Slot
FDD Frequency Division Duplexing
PRACH Physical Random Access Channel
PUCCH Physical Uplink Control Channel
SRS Sounding Reference Signals
TDD Time Division Duplexing
UE User Equipment
UL Uplink
UpPTS Uplink Pilot Time Slot
Appendix A: Detailed UE-to-UE
interference analysis
The deterministic worst case methodology for UE-to-UE interference
analysis with most conservative model can be represented as
• the interfering UE is assumed to operate at maximum transmit power
• the probability factor that the two mobiles do not come in close
proximity of each other.
As a result of such worst case assumptions, the amount of guard
band required for harmonious coexistence based on the deterministic
methodology can be quite prohibitive. In reality, power control is usually
in effect so that the mobile scales down its transmit power due to its
channel conditions and there is a chance of probability that two UEs
come into close distance to cause interference.
On the other hand, there have been some practices to evaluate the
UE-to-UE interference using the traditional Monte Carlo simulation
assuming uniform user distribution within a cell. These studies often
give more optimistic results as the probability of two UEs coming
close to each other under the uniform distribution assumption is very
low, resulting in often negligible performance degradation in terms of
capacity loss. In addition, this approach does not take into account some
real concerns of the operators – the “hot-spot” phenomenon, i.e., high
user density areas such as a coffee shop or a sports stadium.
One potential way forward is to develop a more accurate statistical
modeling for evaluating the UE-to-UE interference under Monte Carlo
simulation. Some of our previous studies have developed a hotspot
based Monte Carlo simulation with non-uniform user distribution
to address these issues and try to strike a balance between the
deterministic worst case analysis and Monte Carlo simulation with
uniform user distribution. Inputs from operators are needed to better
characterize these high user density spots.