ptp 800 with adaptive coding and modulation (acm) · pdf fileptp 800 with adaptive coding and...

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PTP 800 with Adaptive Coding and Modulation (ACM)Maximizing PTP 800 link throughput with Hitless and Errorless ACM

Contents

PAGE 2

Pg Section

3 Executive Summary

4 Introduction

5 ACM Overview

6 Key Benefits of ACM

7 How ACM Works

8 Typical ACM Applications

9 Sample Case Studies

9 Using ACM to Achieve Performance Objectives

10 Case 1: Fixed Mode for Hospital Link

10 Case 2: Increase Hospital Link Throughput

11 Case 3: Minimize Hospital Link Outage

12 Case 4: Use Smaller Antenna for Hospital Link

13 Using ACM to Achieve Greater Range

13 Case 5: Fixed Mode for Sales Office

14 Case 6: Increase the Range of the Sales Office Link

15 Motorola’s Approach to ACM

16 Summary

Executive Summary Organizations of all types have experienced a continuing increase in demand for high-bandwidth wireless communications to support a wide variety of data, voice and video applications. This increasing demand has accelerated the need for high throughput wireless links at a time when most information technology (IT) budgets and staffing have decreased. One way to meet this challenge is to do more with what you have.

Adaptive Coding and Modulation (ACM) technology can help you do just that. Designed to help increase throughput over a radio link while making efficient use of the existing spectrum, ACM functionality adapts coding and modulation rates to changing environmental conditions. With ACM, you can turn fade margin into increased throughput and improve link availability. This capability can provide significant savings in both capital expenditure (CAPEX) and overall operating expenditure (OPEX).

This paper explains how ACM can help you achieve these results with your existing or planned Motorola Point-to-Point (PTP) 800 Wireless Licensed Ethernet Microwave solutions.

Figure 1:PTP 800 Outdoor Unit (ODU) and Compact Modem Unit (CMU)

PAGE 3

Introduction The universal demand for added throughput is being driven by the growth of multimedia applications. Currently, video-dominated content accounts for an ever-increasing percentage of the multimedia mix. Business and government enterprises need high-performance connectivity and backhaul to support bandwidth-intensive applications such as on-demand tutorials, video conferencing, online training, media relations, product demonstrations, Voice-over-IP (VoIP) and video surveillance. At the same time, consumers want access to services such as online gaming, social networking and on-demand television.

Motorola’s PTP 800 Licensed Ethernet Microwave solutions are high-capacity wireless broadband radios designed to efficiently and affordably transport multimedia traffic. However, as with all microwave radios, PTP 800 systems can experience rain fade and multipath interference which can adversely affect microwave transmissions. ACM can eliminate or greatly minimize the effects of rain fade and multipath interference.

Traditionally, licensed microwave radios have supported only the Fixed Modulation mode. However, PTP 800 systems, release 02-00 and higher, support both Fixed Modulation and ACM. In the fixed mode, significant fade margin is reserved during the link planning process to provide adequate link availability in case of rain fade or multipath interference.

Fade Margin = Difference between Mean Receive Signal Level (Rx) and Receiver Threshold at a Given Modulation Mode

Figure 2: Fixed Modulation Fade Margin

Mean rx signal

Level requiredfor 16QAM

Fade marginfor 16QAM

16QAM Avail

16QAM Unavail

When the ACM mode is chosen, the ACM feature can turn reserved fade margin into increased link capacity. Without any hardware change, ACM can maximize throughput by automatically adapting to a higher modulation and coding rate. When a radio is working in a Fixed Modulation mode, a severe rain storm can cause a link outage when the rain fade exceeds the reserved fade margin. In contrast, ACM can keep the link in service and improve the link availability with lower throughput by adapting to a lower modulation mode.

Figure 3: ACM Modulation Modes

256QAM

H256

QAML128

QAM64

QAM32QAM16

QAM8PSKQPSK

PAGE 4

ACM is a standard feature on PTP 800 systems and requires no additional charge. The major advantages of Motorola’s ACM implementation include:• Hitless and Errorless ACM: No bit errors or suspension of traffic flow during modulation shifts• Up to 8 levels of ACM profile; supports QPSK, 8PSK, 16/32/64/128/256 QAM with different coding rates• Quick modulation shifts to cope with up to 100 dB/sec fading • Easy initial setup; no further user intervention• Flexible control; users define the highest and lowest modulation for ACM• Easy link planning with the PTP LINKPlanner tool

ACM Overview ACM is an alternate link adaptation method that promises to raise the overall system throughput and improve the link availability. When ACM is enabled, the radio automatically “up-shifts” and “down-shifts” the modulation and/or coding rate as radio frequency (RF) path conditions change. This enables the radio transmitter and receiver to negotiate the highest mutually sustainable data rate for the path conditions.

In order to achieve high link availability, a typical licensed microwave link reserves 30 to 40 dB for fade margin. For a radio configured to use Fixed Modulation, the radio’s nominal receive signal level will be much higher than the receiver sensitivity threshold of the desired modulation.

For a radio operating in the fixed mode and designed with 99.999% link availability, the average link outage would be 5.3 minutes in a year. This projected outage would be a result of the receive signal level falling below the receiver’s sensitivity threshold. With ACM technology, the radio will down-shift to a lower modulation if the link budget falls below the threshold that the link can sustain.

Let’s consider an example based on a link with a 56 MHz channel operating in the ACM mode. When the RF condition is good, the radio will work at top mode – 256 QAM with a 0.91 coding rate – and deliver 368 Mbps (full duplex) throughput. When the link’s Signal-to-Noise Ratio (SNR) falls below the threshold of 256 QAM with 0.91 coding, the system will switch to the next lower ACM profile – 256 QAM with a coding rate of 0.80 – and deliver 347 Mbps throughput. The switchover will be errorless and hitless, meaning there will be no bit error or traffic flow suspension.

If the fade intensifies, the radio will shift down to the next ACM profile, 128 QAM, and deliver 303 Mbps throughput. Should the RF condition continue to worsen, the modulation will move down step-by-step as the weather condition requires. ACM and enhanced quality-of-service (QoS) control allow high-priority traffic such as voice and real-time services to pass across the link without difficulty.

When the weather condition improves, the radio will automatically switch to the next higher modulation mode. In this case, the radio would shift from 128 QAM back to 256 QAM. Switching is always automatic and performed as quickly as necessary. The PTP 800’s ACM functionality is designed to cope with up to 100 dB of fading per second.

PAGE 5

Introduction continued

Figure 4: ACM Adapting to Weather Conditions

256QAM-H

256QAM-L

128 QAM

64 QAM

32 QAM

16 QAM

8PSK

QPSK

The consequences of a link outage are often multiplied, even when the RF link is lost for only 50 milliseconds. Due to TCP/IP timeout, re-routing and recovery, it could easily take several seconds for a TCP/IP session to be fully recovered. With exceptionally smooth change steps from QPSK to 256 QAM and errorless and hitless coding and modulation, the PTP 800 incurs no service interruption as the modulation steps from one level to another. In this way, ACM can eliminate the link outage time.

Key Benefits of ACM When utilizing ACM technology, you can realize several benefits, including:• I mproved Spectrum Efficiency: Most of the time, the radio will work at top rate mode and provide a

higher average throughput to the end user. • I mproved Link Availability: By shifting to a lower modulation mode and the resulting improvement in

receive signal quality, extra fade margin will be achieved to deliver higher link availability. • Minimal Link Outage Damage: By keeping the link in service with a lower capacity during deep fade

conditions, ACM greatly minimizes the consequences of a wireless link outage due to TCP/IP layer timeout, re-routing and recovery.

• CAPEX and OPEX Savings: On PTP 800 systems, there is no additional cost to enable ACM. Once the easy set-up is completed, no further intervention is required. With Motorola’s PTP LINKPlanner, link planning with ACM can be completed quickly and easily, often in a matter of hours rather than days. Plus, with ACM, the operator has the option to reduce the antenna size and/or connect over a longer distance than with radios operating in a fixed mode.

PAGE 6

ACM Overview continued

How ACM Works Operators can enable ACM radios using the installation wizard from the PTP 800 Graphical User Interface (GUI) web page. There are two parameters that define the range of the modulation modes:• “Max Mod Mode” defines the highest modulation mode at which the radio can operate• “Min Mod Mode” defines the lowest modulation mode at which the radio can operate

Each link direction can adapt the modulation mode independently of the other direction. After the minimum and maximum modulation modes are defined, the “Maximum Tx Power” will be limited by the maximum transmit power of the highest modulation mode.

Latency for a given mode in ACM is the same as for the same mode in Fixed Modulation.

In operation, the radio will adapt between the “Max Mod Mode” and the “Min Mod Mode” based on measurements of received signal quality. As the receive signal quality improves, the radio will adapt to higher modulations which will provide greater throughput. As the receive signal quality deteriorates, the radio will adapt to lower modulations which will provide lower throughput but greater robustness. Each modulation mode has two thresholds: • One threshold for up-shifting when the signal quality improves• One threshold for down-shifting when the signal quality degrades

Figure 5:ACM Thresholds Compared to Fixed Mode

Fixed Mode

ACM

256QAM, Rate 0.83

256QAM, Rate 0.91

64QAM, Rate 0.82

16QAM, Rate 0.91

32QAM, Rate 0.87

8PSK, Rate 0.84

QPSK, Rate 0.80

128QAM, Rate 0.82

Signal-to-Noise Radio (SNR)

To be hitless and errorless during modulation shifts, ACM requires a higher SNR than with the Fixed Modulation mode.

PAGE 7

Typical ACM Applications ACM is designed to improve PTP 800 performance in changing environmental conditions. That improved performance provides significant value for the many varied applications for which PTP 800 systems are deployed, including:

• Building-to-building and campus connectivity • Last-mile extensions• Ethernet data, voice and video communications • Disaster recovery• Backhaul • Wire-line redundancy• Video surveillance • Distance learning• Voice-over-IP (VoIP) • WiMAX and/or LTE backhaul• Leased-line replacement

Businesses, government and educational agencies, health care providers, utility companies, transportation agencies, service providers, carriers and others use PTP solutions to establish or expand their wireless networks. If a radio cannot send and receive information because of rain fade or multipath interference, your wireless link is not doing the full job.

ACM can help you improve link availability and increase throughput without changing hardware. The key is to evaluate your environmental challenges and enable ACM where the technology will help you overcome rain and interference challenges. The following case studies provide detailed information on how ACM can be applied to specific situations and requirements.

Sample Case Studies In the following examples, hypothetical link configurations are presented to illustrate the concept of enabling ACM to help you achieve specific link objectives. During actual system setup, you can decide how to leverage ACM technology to achieve the best possible results for your individual situation.

Sample Cases Results Compared to Fixed Mode Configuration

Case 2 ACM –Hospital Link

• Higher average link throughput• Same link availability• No throughput reduction as compared

with fixed mode

• Keep “Min Mod Mode” the same as with the fixed mode

• Set “Max Mod Mode” to higher modulation than fixed mode

Case 3 ACM – Hospital Link

• Higher average link throughput• Minimized link outage with improved

link availability

• Set “Min Mod Mode” to lowest modulation

• Set “Max Mod Mode” to top modulation rate

Case 4 ACM – Hospital Link

• Higher average link throughput • Same link availability with lower

capacity during deep fade• Cost savings on antenna



• Reduce antenna size

Case 6 ACM – Sales Office Link

• Higher average link throughput• Same link availability with lower

capacity during deep fade • Longer range



Using ACM to Achieve Performance ObjectivesIn the following examples, the link is 5 miles (8 km), requires 99.999% link availability and needs 250 Mbps throughput. For this case, we chose 15 GHz with 56 MHz channel bandwidth.

Figure 6:Hospital-to-Clinic Path Profile

1620

1600

1580

1560

1540

1520

1500

1480

1460

1440

1420

1400

Hospital

0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75

Clinic

Range On Path (miles)

Hei

gh

t A

bo

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ea L

evel

(fe

et)

• Case 1: Fixed Mode for Hospital Link The radio is set to Fixed Modulation mode at 64 QAM with a 4-foot antenna at each end. As shown

below, the link provides 255.22 Mbps throughput with 99.999% link availability.

Figure 7:Case 1 Fixed Mode – Hospital Link Performance

Mode

Max Aggregate

User IPThroughput

(Mbps)

MaxUser IP

Throughput in Either Direction (Mbps)

Hospital Clinic

Fade Margin

(dB)

IP Throughput Availability

(%)

Receive Time in Mode

(%)

Fade Margin

(dB)


(%)


(%)

64QAM 0.82 510.44 255.22 39.98 99.9991 99.9991 39.98 99.9991 99.9991

Link IP Throughput and Availability

Mean IP Throughput Required 250.00 Mbps

Mean IP Throughput Predicted 255.22 Mbps

Percentage of Required IP Throughput 102.09%

Link Symmetry Symmetric

Link Availability 99.9991%

• Case 2: Increase Hospital Link Throughput Now, the objective is to achieve the highest possible throughput with ACM, while still meeting 99.999%

link availability and using the same minimum throughput as for the fixed mode. With no change to the hardware and ACM enabled, the “Min Mod Mode” is set to 64 QAM (the same as for the fixed mode). Then the “Max Mod Mode” is set to 256 QAM with a 0.91 coding rate which will allow the link availability to achieve the required 99.999%. .

Figure 8:Case 2 ACM – Increase Throughput Over Hospital Link

Mode

Max Aggregate

User IPThroughput

(Mbps)

MaxUser IP


Hospital Clinic

Fade Margin

(dB)


(%)


(%)

Fade Margin

(dB)


(%)


(%)

256QAM 0.91 737.30 368.65 24.87 99.9960 99.9960 24.87 99.9960 99.9960

256QAM 0.80 694.38 347.19 24.87 99.9960 0.0000 24.87 99.9960 0.0000

128QAM 0.82 607.04 303.52 31.10 99.9980 0.0020 31.10 99.9980 0.0020

64QAM 0.82 510.44 255.22 37.98 99.9990 0.0010 37.98 99.9990 0.0010







In comparison to the radio performance in the fixed mode, the average link throughput has increased to 368.64 Mbps with the link availability remaining at 99.999%. Throughput has increased by 44% with no hardware change.

PAGE 10

Sample Case Studies continued

When changing from Fixed Modulation mode to ACM, the minimum and maximum modulation modes must be set properly to maintain the same link availability with a guaranteed minimum throughput. The “Min Mod Mode” must remain the same modulation as with the fixed mode and the “Max Mod Mode” needs to be the highest modulation that the link can sustain to meet the link availability requirement. These setup changes can be done easily using the PTP LINKPlanner tool.

• Case 3: Minimize Hospital Link Outage In this example, the objective is to achieve the highest possible throughput with ACM while minimizing

the link outage time. With no change to the hardware and ACM enabled, the “Min Mod Mode” is set to QPSK, and the “Max Mod Mode” is set to 256 QAM with 0.91 coding rate. Based on this configuration, the system performance would be as shown below.

Figure 9:Case 3 ACM – Minimize Link Outage Over Hospital Link

Mode

Max Aggregate

User IPThroughput

(Mbps)

MaxUser IP


Hospital Clinic

Fade Margin

(dB)


(%)


(%)

Fade Margin

(dB)


(%)


(%)

256QAM 0.91 737.30 368.65 24.87 99.9960 99.9960 24.87 99.9960 99.9960

256QAM 0.80 694.38 347.19 24.87 99.9960 0.0000 24.87 99.9960 0.0000

128QAM 0.82 607.04 303.52 31.10 99.9980 0.0020 31.10 99.9980 0.0020

64QAM 0.82 510.44 255.22 34.31 99.9985 0.0005 34.31 99.9985 0.0005

32QAM 0.84 405.52 202.76 37.25 99.9989 0.0004 37.25 99.9989 0.0004

16QAM 0.79 304.88 152.44 41.35 99.9992 0.0003 41.35 99.9992 0.0003

8PSK 0.80 231.70 115.85 43.17 99.9993 0.0001 43.17 99.9993 0.0001

QPSK 0.80 154.30 77.15 50.30 99.9996 0.0003 50.30 99.9996 0.0003







In comparison to the radio performance in the fixed mode, the backhaul currently delivers an average link throughput of 368.64 Mbps and link availability of 99.9996%. The annual link outage time has been reduced from 4 minutes 43 seconds in the fixed mode to 2 minutes 6 seconds in the ACM mode. The fade margin has improved 10.32 dB, and the throughput has increased by 44% with no radio hardware change or antenna change.

PAGE 11


• Case 4: Use Smaller Antenna for Hospital Link In this case, the goal is to use a smaller dish while still maintaining 99.999% link availability and the

highest possible throughput with ACM. With the antenna size reduced from 4 feet (1.2 meters) to 2 feet (0.61 meters) on both ends and ACM enabled, the “Min Mod Mode” is set to QPSK and the “Max Mod Mode” to 256 QAM with a 0.91 coding rate. Using this configuration, the performance would be as shown below.

Figure 10:Case 4 ACM – Smaller Antenna Size for Hospital Link

Mode

Max Aggregate

User IPThroughput

(Mbps)

MaxUser IP


Hospital Clinic

Fade Margin

(dB)


(%)


(%)

Fade Margin

(dB)


(%)


(%)

256QAM 0.91 737.30 368.65 12.73 99.9741 99.9741 12.73 99.9741 99.9741

256QAM 0.80 694.38 347.19 12.73 99.9741 0.0000 12.73 99.9741 0.0000

128QAM 0.82 607.04 303.52 18.96 99.9914 0.0174 18.96 99.9914 0.0174

64QAM 0.82 510.44 255.22 22.17 99.9945 0.0030 22.17 99.9945 0.0030

32QAM 0.84 405.52 202.76 25.11 99.9961 0.0017 25.11 99.9961 0.0017

16QAM 0.79 304.88 152.44 29.21 99.9976 0.0014 29.21 99.9976 0.0014

8PSK 0.80 231.70 115.85 31.03 99.9980 0.0004 31.03 99.9980 0.0004

QPSK 0.80 154.30 77.15 38.16 99.9990 0.0010 38.16 99.9990 0.0010







In comparison to the fixed mode, the average link throughput has increased to 368.62 Mbps, the link availability is still 99.999% and the antenna on each end has been reduced from 4 feet to 2 feet (1.2 meters to 0.61 meter).

PAGE 12


Using ACM to Achieve Greater RangeIn this case, a 2-foot (0.61-meter) antenna is chosen for each end of the link using 7 GHz with 28 MHz channel size.

• Case 5: Fixed Mode for Sales Office With the radio set to 256 QAM, the link can reach 7.7 miles (12.4 km) with 99.999% link availability.

Figure 11:Sales Office Path Profile in Fixed Mode

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5Range On Path (miles)

Hei

gh

t A

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evel

(fe

et)

1620

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1580

1560

1540

1520

1500

1480

1460

1440

1420

1400

1380

Sales Office Warehouse

Figure 12:Case 5 Fixed Mode – Sales Office Link Performance

Mode

Max Aggregate

User IPThroughput

(Mbps)

MaxUser IP



Fade Margin

(dB)


(%)


(%)

Fade Margin

(dB)


(%)


(%)

256QAM 0.80 341.02 170.51 17.13 99.9991 99.9991 17.13 99.9991 99.9991







Link Distance 7.705 miles (12.4 km)

PAGE 13


• Case 6: Increase the Range of the Sales Office Link With no hardware change and ACM enabled, the “Max Mod Mode” is set to 256 QAM and the “Min Mod

Mode” to QPSK, allowing the radio to reach up to 16 miles (25.7 km) with 99.999% link availability.

Figure 13:Sales Office Path Profile in ACM Mode

162016001580156015401520150014801460144014201400138013601340

Sales Office

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Warehouse

Range On Path (miles)

Hei

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evel

(fe

et)

Figure 14:Case 6 ACM – Greater Range for Sales Office Link

Mode

Max Aggregate

User IPThroughput

(Mbps)

MaxUser IP



Fade Margin

(dB)


(%)


(%)

Fade Margin

(dB)


(%)


(%)

256QAM 0.80 341.02 170.51 4.65 98.7407 98.7407 4.65 98.7407 98.7407

128QAM 0.84 302.24 151.12 10.88 99.9108 1.1701 10.88 99.9108 1.1701

64QAM 0.82 250.66 125.33 14.09 99.9645 0.0537 14.09 99.9645 0.0537

32QAM 0.85 202.48 101.24 16.93 99.9827 0.0182 16.93 99.9827 0.0182

16QAM 0.79 149.70 74.85 21.13 99.9935 0.0107 21.13 99.9935 0.0107

8PSK 0.80 113.74 56.87 22.95 99.9956 0.0021 22.95 99.9956 0.0021

QPSK 0.80 75.72 37.86 30.09 99.9991 0.0035 30.09 99.9991 0.0035







Link Distance 16.017 miles (25.7 km)

In comparison to the fixed mode, the link can now reach 16 miles (25.7 km) with an average throughput of 170 Mbps. During deep fade conditions, the link can run on a lower modulation at lower throughput while keeping the link availability at 99.999%.

PAGE 14


Motorola’s Approach to ACM With more than six years of experience in implementing ACM on the PTP 500 and PTP 600 unlicensed radios, we have developed considerable expertise in this area. We know how to engineer hitless and errorless technology with smooth, high-speed modulation shifts. Equally important, “ease of use” has always been a paramount objective for all our Wireless Network Solutions.

In particular, the ACM provided with PTP 800 Licensed Ethernet Microwave solutions has several advantages over comparable systems, including:• Support for QPSK, 8PSK, 16/32/64/128 QAM, 256 QAM with 0.83 coding rate and 256 QAM with 0.91

coding rate – up to eight levels of modulation and coding. • Hitless and errorless modulation – no bit errors or suspension of traffic flow during shifting• Flexible control – operators can define the maximum and minimum modulation modes• Fast shifting – ACM can cope with up to 100 dB/sec fading change• Easy setup – The installation wizard guides operators through a quick configuration procedure. Because

the regulatory rules have been embedded into the link installation wizard, you do not have to worry about violating licensing rules when ACM is enabled. After initial setup, no further user intervention is required.

• Fast, accurate link planning – With PTP LINKPlanner, both the Fixed and ACM modes are supported. Plus, LINKPlanner includes many sophisticated features that greatly reduce link planning man-hours and allow you to easily review and compare performance parameters to configure the solution which best meets your requirements.

Figure 15:PTP LINKPlanner with ACM

Motorola, Inc., 1303 E. Algonquin Road, Schaumburg, Illinois 60196 U.S.A. • www.motorola.com/ptp

MOTOROLA and the Stylized M Logo are registered in the U.S. Patent and Trademark Office. All other product or service names are the property of their respective owners. © Motorola, Inc. 2010. All rights reserved.

GO-23-141WNS PTP 800 ACM SB 062410

Summary The principle of Adaptive Coding and Modulation is simple: to enable uninterrupted communications in poor RF conditions and increase throughput during good RF conditions. ACM accomplishes that by automatically adjusting modulation and/or coding rates to adapt to changes in environmental conditions. In poor conditions, ACM will automatically shift the modulation and/or coding rate to a lower level to maintain an uninterrupted flow of data, voice and video communications. In good conditions, ACM will shift the modulation and/or coding rate to a higher level to deliver faster throughput. In contrast, systems operating in a Fixed Modulation mode are designed for worst-case conditions, resulting in less efficient utilization of the spectrum.

ACM can offer significant benefits, including:• Maximized spectrum efficiency• Increased link capacity• Improved link availability• Reduced antenna size • Extended link distance

In addition, Motorola’s ACM experience and expertise can help you deploy the best solution for your individual situation. Easy-to-use link planning and deployment tools are great time savers for wireless network staffs that are already stretched too thin.

These benefits can help you stretch your wireless dollar much further and help your Motorola PTP 800 solutions work much smarter.

Wireless Network Solutions Motorola delivers seamless connectivity that puts real-time information in the hands of users, giving customers the agility they need to grow their business or better protect and serve the public. Working seamlessly together with its world-class devices, Motorola’s unrivalled wireless network solutions include indoor WLAN, outdoor wireless mesh, point-to-multipoint, point-to-point networks and voice over WLAN solutions. Combined with powerful software for wireless network design, security, management and troubleshooting, Motorola’s solutions deliver trusted networking and anywhere access to organizations across the globe.

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