RF Channel Characterization with Multiple Antenna … RF Channel Characterization with Multiple Antenna Systems for LTE Author: Leonhard Korowajczuk Created Date: 9/18/2012 10:37:18

RF Channel Characterization with Multiple Antenna Systems

for LTE Leonhard Korowajczuk

CEO/CTO CelPlan Technologies

[email protected] www.celplan.com

703-259-4022

9/18/2012 Copyright CelPlan Technologies, Inc. 1

mailto:[email protected]

http://www.celplan.com/

CelPlan Technologies • Planning, Design and Optimization Software for all

applications and network technologies

• Network planning, design an optimization services

• Turnkey deployment of dedicated wireless networks

• Specialized High Level Consulting

• Technical Team Building

• Technology Training

• Business Case Preparation

• CelPlan has design and optimized hundreds of networks of all main technologies around the world


Leonhard Korowajczuk • 45 years R&D, engineering and manufacturing experience in

the telecom field – SESA RIO, STC , BTM – CPqD (Telecom R&D Center) – Elebra/ Alcatel – CEO and CTO CelPlan Technologies – Holds 13 patents

• Published Books – “Designing cdma2000 Systems” published by Wiley in 2006- 963 pages, available in hard cover, e-book and

Kindle – “LTE , WiMAX and WLAN Network Design, Optimization and

Performance Analysis ” published by Wiley (June 2011)- 750 pages, available in hard cover, e-

book and Kindle

• Books in Preparation: – LTE , WiMAX and WLAN Network Design, Optimization and

Performance Analysis- second edition (Wiley) – Network Video: Private and Public Safety Applications (Wiley) – Multi-technology Networks: from GSM to LTE (Wiley) – Backhaul Network Design (Wiley) – Smart Grids Network Design


Questions that do not have replies today

• What is network’s RF channel response?

– How wide and long is the multipath fading?

– How many multipath are being received?

• How un-correlated are cell antennas?

– How to adjust the antennas for maximum un-correlation?

• What is the channel load and how are the resources distributed?

• How should the network parameters be optimized?


CelSDRx™ • Universal Software Defined Receiver (SDRx) • Captures up to 100 MHz of spectrum from 100 MHz to 18 GHz • Digitizes signal at 125 Msps and provides I and Q components • Digitally extracts information for any digital technology: LTE, WiMAX, HSPA, UMTS,

GSM • Implemented for LTE

– Performs • Symbol synchronization • Frame Synchronization • Sub-Channel Equalization • Bandwidth and frame number determination

– Detects • RF Channel Response in time and frequency

– Displays fading amplitude, band and duration

• Channel Traffic load • Received signal coherence from different antennas • Received signal coherence to different antennas

• GPS data geo-referencing, allowing drive tests • Ideal to plan network parameters • Ideal to scan competitive networks • Patents applied


CelSDRx ™ Specifications • Frequency coverage: 100 MHz to 18 GHz • Instantaneous Bandwidth: 100 MHz • Displayed Average Noise Level:

• -115 dBm @ 10 MHz • -110 dBm @ 1500 MHz • -110 dBm @ 2500 MHz

• Maximum RF input: +10 dBm • Non-input related spurs: < -100 dBm • Maximum RF gain: 20 dB • IF gain: -10 to +30 dB in 1 dB steps • Power Supply +12 VDC


• Subcarrier spacing: 15 kHz • Frame Duration: 10 ms • Sub-Frame duration: 1ms • Slot Duration: 0.5 ms • Slot: 6 or 7 Symbols


LTE Downlink Frame

LTE Downlink Frame Detail • PSS (Primary Synchronization Signal)

• SSS (secondary Synchronization Signal)

• PBCH (Physical Broadcast Channel

• RS (Reference Signals)

• Control Channels

• Data Channels

• Resource Element


Reference Signals

• Each antenna transmits its own reference signals (RS)

• An antenna does not transmit in the slots dedicated to the other antenna symbols

• The exact position of the RS for an antenna depends on the CellID


12 sub-carriers

Normal CPExtended CP

Eve

n S

lot (0

.5 m

s)

2 S

lots

(1

ms)

Od

d S

lot (0

.5 m

s)

Antenna Port 0

Antenna Port 1

Antenna Port 2

Antenna Port 3

Symbol

12 sub-carriers

Resource Element and Resource Block • A Resource Element (RE) is defined by one sub-carrier and 1 symbol • A Resource Block (RB) is defined by 12 consecutive sub-carriers and 1 slot

duration • Short Cyclic Prefix: 12 sub-carriers x 7 symbols: 84 RE • Long Cyclic Prefix: 12 sub-carriers x 6 symbols: 72 RE • The smallest allocation for data transmission is one TTI (Transmission Time

Interval): 1 ms (1 sub-frame/ 2 slots/2 RB) • Several RE are reserved for Reference Signals and Control Channels

12 sub-carriers

7 s

ym

bo

ls

0.5 ms

1 slot6

sym

bo

ls

12 sub-carriers

0.5 ms

1 slot


LTE Measurement Capabilities • Bandwidth: 1.4 – 20 MHz • FDD and TDD • Measurements

– PSS Power/ Quality – SSS Power/Quality – Physical Layer Cell Identity Group – MIB detection (Bandwidth and Number of Antennas) – Reference Signal Received Power/Quality (RSRP) – Wideband Spectral Display with Marker Functions – Power vs. Time vs. Frequency – Average RSSI – Channel Impulse Response and Power Delay Profile – Number of Multipath Components – RF Channels Response – Antenna Correlation

• Measurements are time stamped and Geo-referenced


LTE Signal Capture Example

• Band: 700 MHz

• Verizon (Block C)

• Channel Bandwidth: 10 MHz

• Total Sub-carriers: 667

• Used Sub-carriers: 600


Steps • Set frequency and

capture bandwidth • Capture 200 ms • Extract baseband signal

I and Q • Apply FFT • Search for PSS

– Establish part of cell ID

• Search for SSS – Establish Cell ID – Synchronize frame

start and symbols

• Generate RS • Detect RS


• Obtain RF channel response

• Calculate RF channel response for RS signals

• Interpolate RF channel response for other symbols

• Adjust all symbol values

• Extract PBCH values

– MIB

– Channel bandwidth, number of antennas, cyclic prefix

– Frame number

• Obtain frame map

• Correlate frames


Average Sub-carrier Power per Frame (dBm)


Average OFDM Symbol Power per Band (dBm)

Impulse Response


Measured Power per Resource Element (dBm)


RF Channel Response (top view)


RF Channel Response (time zoom)


RF Channel Response (frequency and time zoom)


RF Channel Response (3D detail)


Adjusted Power per Resource Element (dBm)


Traffic view • Traffic allocation can be visualized per frame


Correlation • Correlation is considered as the sympathetic movement of two or

more variables • Pearson’s Product-Moment Correlation Coefficient

– The correlation coefficient varies between +1 and -1 • Positive Correlation: movement is in the same direction • Negative Correlation: movement is in the opposite direction

• Reference signals transmitted by two antennas can be used to establish the channel response

• The correlation coefficient for the two channel responses can then be calculated


Correlation between antennas • Correlation index between two antennas

CI=0.42


Antenna Correlation Drive • Antenna correlation variation


Conclusion

• CelSDRx ™ promises to be an important tool to evaluate the RF channel performance and tune systems with multiple antennas. – It will increase network throughput and reduce

interference

• A side benefit is the ability of evaluating traffic loads

• The flexibility of Software Defined Receivers is essential for the complex digital systems being deployed


Documents

RF Channel Characterization with Multiple Antenna … RF Channel Characterization with Multiple Antenna Systems for LTE Author: Leonhard Korowajczuk Created Date: 9/18/2012 10:37:18