PTP 800 with Adaptive Coding and Modulation (ACM)

Transcription

1 SOLUTION BRIEF PTP 800 with Adaptive Coding and Modulation (ACM) imizing PTP 800 link throughput with Hitless and Errorless ACM

2 Contents 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 for Hospital Link 10 Case 2: Increase Hospital Link 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 for Sales Office 14 Case 6: Increase the Range of the Sales Office Link 15 Motorola s Approach to ACM 16 Summary PAGE 2

3 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 m Unit (CMU) PAGE 3

4 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- (Vo) 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 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. = Difference between Mean Signal Level (Rx) and r Threshold at a Given Modulation Mean rx signal Figure 2: Fixed Modulation Level required for 16QAM margin for 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 s 8PSK QPSK 16 QAM 32 QAM 64 QAM 128 QAM 256 QAM L 256 QAM H PAGE 4

5 Introduction continued 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 % 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 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

6 ACM Overview continued 256QAM-H 256QAM-L Figure 4: ACM Adapting to Weather Conditions 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/ timeout, re-routing and recovery, it could easily take several seconds for a TCP/ 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 : 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/ 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

7 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: Mod defines the highest modulation mode at which the radio can operate Min Mod 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 imum 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 Mod and the Min Mod 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 256QAM, Rate QAM, Rate QAM, Rate QAM, Rate 0.82 Figure 5: ACM Thresholds Compared to Fixed 32QAM, Rate QAM, Rate PSK, Rate 0.84 Fixed ACM QPSK, Rate 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

8 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 Ethernet data, voice and video communications Backhaul Video surveillance Voice-over- (Vo) Leased-line replacement Last-mile extensions Disaster recovery Wire-line redundancy Distance learning WiMAX and/or LTE backhaul 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. PAGE 8

9 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 Configuration Case 2 ACM Hospital Link Case 3 ACM Hospital Link Case 4 ACM Hospital Link Case 6 ACM Sales Office Link Higher average link throughput Same link availability No throughput reduction as compared with fixed mode Higher average link throughput Minimized link outage with improved link availability Higher average link throughput Same link availability with lower capacity during deep fade Cost savings on antenna Higher average link throughput Same link availability with lower capacity during deep fade Longer range Keep Min Mod the same as with the fixed mode Set Mod to higher modulation than fixed mode Set Min Mod to lowest modulation Set Mod to top modulation rate Set Min Mod to lowest modulation Set Mod to top modulation rate Reduce antenna size Set Min Mod to lowest modulation Set Mod to top modulation rate Using ACM to Achieve Performance Objectives In the following examples, the link is 5 miles (8 km), requires % 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 Height Above Sea Level (feet) Hospital Clinic Range On Path (miles) PAGE 9

10 Sample Case Studies continued Case 1: Fixed 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 Mbps throughput with % link availability. Figure 7: Case 1 Fixed Hospital Link Performance 64QAM 0.82 Aggregate User User in Either Direction Hospital Clinic Mean Required Mean Predicted Link and Mbps Mbps Percentage of Required % Link Symmetry Symmetric Link % Case 2: Increase Hospital Link Now, the objective is to achieve the highest possible throughput with ACM, while still meeting % 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 is set to 64 QAM (the same as for the fixed mode). Then the Mod is set to 256 QAM with a 0.91 coding rate which will allow the link availability to achieve the required %.. Figure 8: Case 2 ACM Increase Over Hospital Link 256QAM QAM 128QAM QAM 0.82 Aggregate User User in Either Direction Hospital Clinic Mean Required Mean Predicted Link and Mbps Mbps Percentage of Required % Link Symmetry Symmetric Link % In comparison to the radio performance in the fixed mode, the average link throughput has increased to Mbps with the link availability remaining at %. has increased by 44% with no hardware change. PAGE 10

11 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 must remain the same modulation as with the fixed mode and the Mod 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 is set to QPSK, and the Mod 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 256QAM QAM 128QAM QAM QAM QAM PSK QPSK Aggregate User User in Either Direction Hospital Clinic Mean Required Mean Predicted Link and Mbps Mbps Percentage of Required % Link Symmetry Symmetric Link % In comparison to the radio performance in the fixed mode, the backhaul currently delivers an average link throughput of Mbps and link availability of %. 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 db, and the throughput has increased by 44% with no radio hardware change or antenna change. PAGE 11

12 Sample Case Studies continued Case 4: Use Smaller Antenna for Hospital Link In this case, the goal is to use a smaller dish while still maintaining % 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 is set to QPSK and the Mod 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 256QAM QAM 128QAM QAM QAM QAM PSK QPSK Aggregate User User in Either Direction Hospital Clinic Mean Required Mean Predicted Link and Mbps Mbps Percentage of Required % Link Symmetry Symmetric Link % In comparison to the fixed mode, the average link throughput has increased to Mbps, the link availability is still % and the antenna on each end has been reduced from 4 feet to 2 feet (1.2 meters to 0.61 meter). PAGE 12

13 Sample Case Studies continued Using ACM to Achieve Greater Range In 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 for Sales Office With the radio set to 256 QAM, the link can reach 7.7 miles (12.4 km) with % link availability. Sales Office Warehouse 1620 Figure 11: Sales Office Path Profile in Fixed Height Above Sea Level (feet) Range On Path (miles) Figure 12: Case 5 Fixed Sales Office Link Performance 256QAM Aggregate User User in Either Direction Sales Office Warehouse Link and Mean Required Mbps Mean Predicted Mbps Percentage of Required % Link Symmetry Symmetric Link % Link Distance miles (12.4 km) PAGE 13

14 Sample Case Studies continued Case 6: Increase the Range of the Sales Office Link With no hardware change and ACM enabled, the Mod is set to 256 QAM and the Min Mod to QPSK, allowing the radio to reach up to 16 miles (25.7 km) with % link availability. Sales Office Warehouse Figure 13: Sales Office Path Profile in ACM Height Above Sea Level (feet) Range On Path (miles) Figure 14: Case 6 ACM Greater Range for Sales Office Link 256QAM 128QAM QAM QAM QAM PSK QPSK Aggregate User User in Either Direction Sales Office Warehouse Mean Required Mean Predicted Link and Mbps Mbps Percentage of Required % Link Symmetry Symmetric Link % Link Distance 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 %. PAGE 14

15 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 PAGE 15

16 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: imized 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. Motorola, Inc., 1303 E. Algonquin Road, Schaumburg, Illinois U.S.A. 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 All rights reserved. WNS PTP 800 ACM SB GO