Overview

This essay discusses how to urge video over wireless performance. Many companies have been regulating assorted latest video calm technologies right away such as live video streaming, webcasting, video conferencing as good as web conferencing. YouTube services go upon to be renouned as good as have been regulating increasingly some-more bandwidth as companies work video for precision as good as selling purposes. Google denunciation interpretation work can right away modify text, creation a English calm formed videos accessible to alternative countries as well. Keep in thoughts which with a proliferation of association VPNs for confidence purposes, employees can work wireless during work as seamlessly as during home or upon a open network. They can entrance a same video services from anywhere. This is because wireless is so renouned right away as good as a need for video category wireless infrastructure performance.

The tide 80.11a/g wireless entrance indicate is simply swamped when multiform clients begin downloading vast files as good as regulating video applications. The many appropriate fortitude for guaranteeing excusable video opening is right away a 802.11n wireless standard. According to a Cisco foresee study, a array of wireless inclination will surpass successive inclination upon a internet by 2015 as good as comment for 54% of IP traffic. In serve video trade will comment for 90% of a consumer internet trade by 2015.

Video Basics

Video as good as voice have been real-time trade streams by inlet which have been supportive to network overload which causes latency (delay). Video has both a interpretation as good as an audio component. It should be remarkable which a same opening metrics such as jitter, latency, parcel detriment as good as throughput start video as good as voice trade opposite a internet as good as association network. Packet detriment has a larger outcome upon video whilst latency affects voice many more. Guaranteeing specific work levels for video upon a network could engage implementing QOS, augmenting network bandwidth, network settlement changes as good as apparatus changes. All these improvements have been for a role of creation a network “video ready”. Companies increasingly work web conferencing, webcasts as good as video conferencing for meetings as good as for precision purposes. Colleges work it to broach courses as well. It is a really price in outcome apparatus to diminution association ride costs.

Types of Video

It is worth deliberating a assorted sorts of video services renouned right away as good as where, from a networking perspective, consumers source a content. Note how many of a services have been opposite a internet.

•Live Video Streaming over a internet of association Webcasts as good as TV broadcasts typically delivered to your desktop.
•Web Conferencing to a desktop with applications such as Skype as good as a really renouned Go to Meeting service.
•Video Conferencing work which runs from as good as opposite a association network with Cisco Telepresence as good as apparatus from companies such as Tandberg as good as Polycom.
•Progressive Video download from companies such as YouTube to a desktop.
•Broadcast Video multicast of a singular to many video streams such as Netflix.

Video Performance

H.323 defines a apartment of protocols for audio as good as video trade together with H.264 as good as G.729 protocols. It is a horizon for have up multimedia applications upon a association network. The G.729 custom is a renouned audio codec for compressing audio trade during 8 Kbps with a 10 ms delay. The H.264 video codec customary is a many tide adopted video focus standard. It specifies 24, thirty as good as 60 frames per second (fps) for tall clarification (HD) video conferencing with focus from 1.5 Gbps of video trade to 4 Mbps during a fortitude of 1920 x 1080 as good as thirty fps.

It is critical to assimilate a opening metrics which start video opening together with parcel loss, latency, jitter as good as throughput. Video is sent as a consistent tide of trade in contrariety to interpretation trade such as email which can be re-transmitted with a little check as good as have no poignant outcome upon work level. Congestion is a simple sign of a network which is bustling as good as experiencing network opening problems. The queues have been busier during times of augmenting network activity. This causes augmenting latency, jitter, parcel loss, decreased throughput as good as re-transmission of packets. Implementing peculiarity of work (QOS) will infrequently radically means forsaken interpretation packets to forestall voice/video parcel loss. The interpretation packets have been afterwards re-transmitted with a little delay. The following defines these attention customary opening metrics.

Latency: Amount of time for a parcel to ride from source to destination

Jitter: Amount of normal movement in latency of any packet

Packet Loss: Percent of packets forsaken from source to destination

Throughput: Average array of packets sent during a bound duration of time

Each video work requires opposite amounts of bandwidth. Some services such as video conferencing have been some-more influenced by augmenting latency, parcel detriment as good as jitter than desktop applications. For excusable video conferencing performance, a parcel detriment should not surpass 1%, jitter thirty ms as good as a one-way latency of 300 ms (latency of 150 ms for tall clarification video conferencing resolution). When these thresholds have been exceeded a settlement can deteriorate. Bandwidth mandate for video have been related to a specific sort of service, volume of fortitude as good as frames per second. For e.g. a customary video conferencing fortitude of 704 x 576 during thirty fps requires 768 Kbps – 1 Mbps of bandwidth whilst a High Definition (HD) fortitude of 1080 x 1920 during thirty fps requires 4 Mbps – twelve Mbps. Desktop services such as streaming video as good as web conferencing have reduce bandwidth mandate than video conferencing, however a same latency, jitter as good as parcel detriment problems start video performance. In serve with all services, we have to supplement an normal of 20% one some-more bandwidth beyond for Ethernet as good as IP custom processing.

Video Quality of Service (QOS)

Implementing peculiarity of work (QOS) upon a association network is an finish to finish routine starting with a video tide source. Video conferencing finish points have been mostly successive to a association corner switch whilst video streaming to a desktop is internet based. The routine of implementing any QOS involves prioritizing trade for favoured service. Considering video conferencing, a Cisco 3560 as good as 3750 entrance corner switches have been mostly used to bond video equipment. The covering 2 interpretation await has an 802.1p header with 3 pieces which can be set for 8 opposite category of work (CoS) values from 0 – 7. For e.g. video is reserved CoS of 4 whilst voice packets have been reserved CoS of 5 as good as a aloft array gets softened service. High priority interpretation is mostly reserved CoS of 2.

DSCP is a covering 3 QOS custom used to mention assorted sorts of work (ToS) classes for data, voice as good as video traffic. DSCP values have been covering 3 as good as as such have been set in a initial 6 pieces of a IP Precedence domain of a IP header. The many appropriate work letter of reference from Cisco for imprinting video is a DSCP of AF41. Data trade is reserved a reduce priority such as AF21 for e.g. whilst voice is reserved a aloft priority of DSCP EF. Video trade is personal with entrance lists which conclude video trade as good as a category map is tangible for video which matches an entrance list as good as points to a specific routine map. The routine map does a DSCP imprinting of video trade as good as a DSCP worth is reserved to a queue. Class of work (CoS) packets can be set with a routine map however it is mostly noted during entrance switches with SRR as good as with WRR during distribution/core switches.

Shaped Round Robin (SRR) is a hardware formed queuing technique deployed with entrance switches. SRR allows covering 2 category of work (CoS) as good as covering 3 (ToS) mappings to queues. The placement as good as core network layers typically have 6500 Cisco switches as good as they work Weighted Round Robin (WRR) hardware queuing. WRR is a same thought however a queuing settlement is rather opposite as good as usually covering 2 category of work values have been mapped to queues.

WAN routers have been deployed with Low Latency Queuing (LLQ) as good as Class Based Weighted Fair Queuing (CBWFQ) which assigns video trade to a tall priority reserve with a specific priority commission such as 15%. That guarantees all video trade will get 15% of a couple bandwidth. For e.g. a 1 Gbps Metro Ethernet circuit will allot 150 Mbps of bandwidth to video trade reduction custom overhead. Company WAN links as a many appropriate work should never surpass we estimate 33% of accessible bandwidth for all voice as good as video traffic. That leaves room for custom beyond as good as interpretation packets. Data trade opening worsens as packets have been forsaken as good as video trade QOS becomes reduction effective.

Desktop applications work a same QOS collection however a association internet tie as good as a wireless network means in to a design. In serve a open wireless network we start to be regulating affects a altogether video network performance. The bandwidth of your home internet tie as good as overload affects opening as good as any overload points opposite a network. The wireless network is many mostly where video opening degrades quite upon an 802.11b open network.

Wireless Standards

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These report a attention customary wireless protocols right away deployed.

80.11b

This wireless customary authorized in 1999 specifies a extent interpretation rate of eleven Mbps regulating a 2.4 GHz unlawful rope in a United States. The rope operate a lot of division from blurb inclination regulating which frequency. The customary in a United States assigns eleven channels with bandwidth of around 80 MHz during 5 MHz per channel. The United States allocates 3 non-overlapping channels of 1, 6 as good as eleven with a core bulk subdivision of twenty-five MHz per channel. The modulation intrigue used with 802.11b is Direct Sequence Spread Spectrum (DSSS) with CCK with characteristics which minimize goods compared with interference. The 802.11b one some-more interpretation rates embody 1, 2, as good as 5.5 Mbps.

802.11g

This wireless customary authorized in 2003 specifies a extent interpretation rate of 54 Mbps regulating a same 2.4 GHz rope as 802.11b. The 802.11g customary is renouned with aloft throughput as good as augmenting coverage. The same division problems start however with a 2.4 GHz band. The 802.11g is concordant with a 802.11b customary as good as assigns a same eleven channels with 1, 6 as good as eleven as non-overlapping. The modulation intrigue used with 802.11g is OFDM which specifies aloft interpretation rates. The one some-more 802.11g interpretation rates embody 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36 as good as 48 Mbps.

802.11a

This wireless customary was authorized in 1999 naming a extent interpretation rate of 54 Mbps regulating a 5 GHz unlawful rope in a United States. The worth of 802.11a is aloft throughput however a dungeon coverage is not as big as good as one some-more entrance points will be indispensable for a same 802.11g coverage. There is many reduction division from inclination such as cordless phones, bluetooth devices, microwaves as good as blurb inclination regulating a 2.4 GHz band. There have been twenty-three non-overlapping channels with a tide 802.11h specification. Some Cisco inclination await both 2.4 GHz as good as 5 GHz transmitters upon a same entrance point. The modulation intrigue used with 802.11a is OFDM, with aloft interpretation rates as good as minimizing goods of interference. Each nation specifies a array of channels as good as frequencies it allows with a 5 GHz band.

802.16

This is a civil (MAN) wireless customary which provides home as good as commercial operation clients seamless wireless entrance from anywhere. The line of steer record specifies a stretch of around twenty-seven miles as good as speeds of up to 120 Mbps. The indicate to multipoint selection operates in a 10-66 GHz range. There is an 802.16a selection with filigree topologies as good as non-line of steer with frequencies from a protected as good as unlawful 2 GHz as good as eleven GHz rope during a speed of 70 Mbps. The pass complaint with any MAN you do regulating unlawful frequencies is division from identical devices.

802.11n

The latest 802.11n wireless customary authorized in 2009 defines many faster interpretation rates of 300 – 600 Mbps as good as 1000 Mbps from entrance indicate to network switch augmenting throughput from customer to entrance indicate as good as entrance indicate to network switch. It operates in both a 2.4 GHz as good as 5 GHz bands with in outcome latest opening enhancements such as churned submit churned outlay (MIMO) as good as channel bonding.

Wireless Contention

Access points have been radically a reduction fit heart character usual media device with a prosaic promote domain. Contrast which with a Cisco Ethernet switch which has 100/1000 Mbps bandwidth per pier as good as promote segmentation with VLANs. The switch uses a many some-more in outcome media entrance row intrigue than wireless entrance points. The wireless network employs an comparison reduction in outcome conduit clarity churned entrance with incident deterrence (CSMA/CA) routine to conduct customer entrance to a network. The outcome of CSMA/CA is augmenting bandwidth usage, parcel detriment as good as parcel re-transmits with this usual media. In serve there have been a customary wireless problems with a 2.4 GHz rope division as good as multipath vigilance blur which occurs when a vigilance bends or is twisted by a have up structure. From a unsentimental viewpoint 15-25 wireless clients can join forces with with a singular entrance indicate during anytime as good as still say good performance. This of march changes as some-more video as good as tall bandwidth applications have been used. The 802.11n can radically await all of those clients regulating simulataneous live video streaming with fourteen of them regulating tall clarification video streams.

Data Rate, Distance as good as Frequency

So by right away we know there is no diverge speed with comparison wireless. Data rate (speed) as good as opening metrics diminution as a wireless clients pierce serve from a entrance point. Beyond an normal of 50-60 feet, a speed decreases as good as latency, parcel detriment as good as jitter increase. The wireless network site consult determines where as good as how many entrance points should be deployed so any dungeon (defined coverage area) has a vigilance strength with 54 Mbps. The coverage area can be lengthened with a stronger directional antenna. For instance, these have been estimate rated distance, speed as good as bulk specifications indoor for a Cisco 1240AG entrance point. Note a 802.11a stretch is typically half which of an 802.11g air wave however this rating was with a stronger 3.5 dBi antenna.

802.11a (5 GHz): 54 Mbps @ 60 ft – 80 ft with 3.5 dBi omnidirectional antenna

802.11g (2.4 GHz): 54 Mbps @ 80 ft – 100 ft with 2.2 dBi dipole antenna

As a interpretation rate increases your in outcome network operation decreases. Clients which wish a successive extent bandwidth will need to muster some-more entrance points per design. Increasing broadcast energy will radically diminution network operation during aloft interpretation rates whilst augmenting a operation with reduce interpretation rates such as a box with 802.11g entrance points. The complaint is with augmenting broadcast power, a receiver attraction decreases with a routine called blunder matrix magnitude. That doesn’t request to a wireless clients where broadcast energy should be set during extent for many appropriate results. The network length or wireless extent stretch is around 100 meters from customer to entrance point, as good as with Ethernet successive designs 100 meters from entrance indicate to switch. The campus settlement can be lengthened with one some-more switch – switch connectivity of course.

Wireless interpretation rates mention extent throughput however which isn’t a unsentimental value. Mixed environments such as 802.11b as good as 802.11g will diminution throughput for both clients upon a same network segment. As referred to a 802.11b as good as 802.11g clients have been concordant as good as can join forces with with a same entrance indicate regulating a 2.4 GHz rope spectrum. Throughput for 802.11b is around 6 Mbps however which will change with receiver type, stretch from a entrance indicate as good as broadcast power. Configure a entrance indicate with 54 Mbps for 802.11g clients as good as simple eleven Mbps for a 802.11b clients. That prevents a entrance indicate from handling during reduction than eleven Mbps. Some entrance points can work with twin rope 802.11a as good as 802.11g however they have been apart judicious networks as good as contingency have apart wireless site surveys. The 802.11a entrance indicate uses a 5 GHz bulk band. As bulk wavelength increases a network operation will decrease. The settlement with 802.11a covers many reduction stretch compared with 802.11g during a same interpretation rates. The aloft bulk (5 GHz) signals do not pass by a have up have up as easy as reduce frequencies.

These have been a little normal bandwidth throughput values as good as compared wireless standards. From a unsentimental viewpoint all twenty-four channels won’t be accessible with a 802.11h customary as good as 802.11a entrance points due to channel overshoot interference. Note a outcome of churned sourroundings wireless apparatus such as 802.11b/g upon a same network as good as decreased throughput. This occurs as good when there have been 802.11n entrance points with comparison entrance points upon a same network.

802.11b – 6 Mbps x 3 channels

802.11g – twenty-two Mbps x 3 channels

802.11b/g – 8 Mbps x 3 channels

802.11a – twenty-five Mbps x twenty-one channels

802.11n – 150 Mbps/300 Mbps x twenty-one channels

Decreasing a broadcast energy of an entrance indicate will minimize channel interference. The in outcome network operation can be lengthened with repeater entrance points, augmenting entrance indicate broadcast energy or adjusting a entrance indicate position. Using a aloft benefit receiver upon a entrance indicate is an choice as well. Cisco entrance points have a lot of options for deploying antennas with aloft benefit as good as sensitivity. Note we should minimize a wire length of any antenna. The longer receiver cabling will draw a signals. Some countries extent a extent entrance indicate broadcast energy setting.

RF Propagation

As referred to vigilance attenuation is worse during aloft frequencies. There is however a lot of environmental factors which distort, hook as good as minimize vigilance strength. The outcome is something called multipath vanishing where a vigilance takes multiform paths to a destination. These have been a little examples.

• Diffraction – vigilance tortuous due to have up have up angles

• Refraction – environmental factors such as steam can means vigilance to bend

• Reflection – water, potion or any well-spoken aspect can rebound a vigilance distorting or vanishing it

• Absorption – structures interesting vigilance (trees)

• EMI division – cordless phones, x-ray ovens, electrical motors, bluetooth devices

Fade Margin is a volume of receiver attraction energy which can be decreased whilst progressing excusable network performance. That is a means with deployment of outward wireless bridges with indicate to indicate topologies such as buildings upon a campus. Problems with sleet will draw signals as good as meaningful a blur domain will equivocate opening issues. Polarization is a course of a radiated settlement from a receiver as good as similar to a pass contingency compare with transmitting as good as reception antenna. The many mostly polarization used with entrance indicate receiver is linear. Antenna can broadcast plane or a straight polarized signal.

Improving Video over Wireless Performance

When deliberating bandwidth mandate as good as assorted video services it is critical to note which a wireless network will regularly need many some-more bandwidth than your association LAN or your home internet tie for a same video service. An e.g. is tall clarification live video streaming where a tangible wireless bandwidth indispensable is many aloft compared with a LAN or home cable/DSL internet connection. The home internet tie would need 500 Kbps – 1 Mbps. That is not a complaint even for home internet where a wire download speed is an normal 10 Mbps. The wireless network with entrance row as good as multipath vanishing problems aren’t as fit as good as would work an in outcome bandwidth of 5 – 10 Mbps. In addition, note which parcel detriment does start video over wireless opening some-more than latency as good as jitter however all metrics can be softened with a following endorsed improvements.

1. Deploy a latest 802.11n Access Point as good as Client Adapters

The latest 802.11n wireless entrance indicate is right away rated during 300 Mbps with a latest underline enhancement. That is 6x faster than a nearest 802.11g standard. Deploying 802.11n in a 5 GHz rope as good as we have twenty-one non-overlapping channels accessible as well. That allows for aloft interpretation rates per coverage area. The latest enhancements embody churned submit churned outlay (MIMO), channel bonding, MAC retard acknowledgment, cargo optimization as good as unicasting as good as QOS prioritizing of trade classes.

MIMO Explained

802.11n uses churned input/output antennas upon a entrance indicate as good as wireless customer to enlarge interpretation rates as good as diminution re-transmits as good as parcel loss. The entrance indicate as good as clients can send coexisting trade streams augmenting a volume of interpretation as good as fluctuating a network operation (distance). The tide many renouned Cisco 1250 AP uses what is called a 2T x 3R MIMO. That is 2 broadcast receiver upon a entrance indicate as good as 3 embrace receiver upon a client. The many appropriate formula start when all wireless clients work 802.11n adapters as good as entrance points have been all 80.11n with no churned sourroundings of 802.11a/g entrance points.

Channel Bonding

The technique of channel fastening right away allows mixing of 2 non-overlapping channels in a 5 GHz rope to send interpretation during 2x a customary interpretation rate for a fanciful 300 Mbps. In work a normal interpretation rate has been tested during 180 Mbps as good as 140 Mbps for video streaming. That is flattering considerable compared with 802.11g normal throughput of twenty-two Mbps.

Payload Optimization

The underline of cargo optimization or parcel assembly is fundamentally putting some-more interpretation in any parcel sent ensuing in some-more in outcome work of a ride media.

MAC Block Acknowledgment

Previous entrance points compulsory which any MAC covering MPDU parcel was alone concurred with an ACK packet. The latest 802.11n customary right away uses a singular retard ACK to admit churned MPDUs. This decreases a volume of custom beyond as good as reduction bandwidth required.

Multicast to Unicast Traffic

Video over wireless presents a specific complaint with multicasting which a successive universe doesn’t have. Wireless entrance points do not await multicasting however 802.11n can right away modify multicast to unicast streams per wireless customer during covering 2.

2. Network Design

The wireless entrance points should regularly be successive to a 100 Mbps full duplex switch port. The 802.11n entrance points should be successive to a 1 Gbps or 10 Gbps switch port. Video finish points should be successive closer to a placement covering as good as upon a reduction bustling line card. The finish indicate video source apparatus can be located during a network corner as well, however we should name a switch with all a opening facilities as good as preferably located in a interpretation center. Wireless churned SSIDs should regularly be tangible to shred trade as good as reserved VLANs to compare a same VLAN schema implemented upon a successive network.

Use a hierarchical settlement with any latest wireless/wired deployments as good as where probable widespread out as good as bond entrance points opposite churned network switches instead of a singular switch. Consider you do a little opening monitoring upon a network to discharge media mismatches. For e.g. a network switch with a Gigabit pier which is uplinked to a switch with a 100 Mbps interface. As good WAN circuits have been many mostly a slowest couple compared with a switch infrastructure.

•Have a correct wireless network site consult finished for any rope to minimize vigilance overshoot as good as optimize coverage.
•Deploy inner customer adapters instead of outmost USB character during your laptop for many appropriate performance.
•When deploying 802.11a/b/g entrance points (mixed environment) with 802.11n entrance points, it is softened to allot a 802.11n entrance points as good as clients to a 5 GHz rope where there is some-more non-overlapping channels as good as reduction interference.
•Use all 802.11n entrance points as good as clients where probable instead of churned sourroundings as good as during slightest 2T x 3R x 2S spatial streams.
•Use one some-more entrance points per coverage area with 802.11n during 5 GHz for augmenting interpretation rate, operation (distance), array of clients as good as network availability.
•Deploy some-more absolute lengthened operation antennas to enlarge a interpretation rate as good as range.
•Clean up problems with any sub-optimal routing upon a network.
•Consider deploying a WLC 4400 WLAN controllers. This requires a firmware ascent upon all 1100 as good as 1200 array unconstrained entrance points, however there have been advantages such as modernized RF government features.

3. End to End Quality of Service (QOS)

Any good peculiarity of work deployment contingency cruise both successive as good as wireless QOS techniques for guaranteeing finish to finish performance. The successive QOS has already been discussed here with Shared Round Robin (SRR) as good as Weighted Round Robin (WRR) hardware queuing upon switches. As good there is Low Latency Queuing (LLQ) as good as Class Based Weighted Fair Queuing (CBWFQ) implemented upon WAN routers. DSCP as good as CoS parcel imprinting is used to prioritize specific trade sorts for favoured queuing. Wireless right away has Wireless Multimedia Extensions (WMM) which classifies trade with 4 categories according to trade type. These embody voice, video, many appropriate bid as good as background. This provides a upon trial work turn for video trade during times of network congestion.

The covering 2 interpretation await from a switch has an 802.1p domain where a category of work (CoS) pieces have been set. The entrance indicate examines which domain as good as queues trade with a specific CoS sourroundings to a reserved queue. The voice trade reserve is a top priority reserve as good as any trade queued there is serviced prior to video as good as data. Any wireless clients not regulating VoIP will have video prioritized first. Note which nonetheless reserve 3 many appropriate bid has a CoS of 0 which reserve is still aloft priority than credentials traffic. Cisco VideoStream focus covering encouragement allows choice of video trade to a priority tide according to a VLAN or SSID choice for favoured queuing.

Access Point Priority Queuing:

Queue 1: Voice Traffic CoS = 6,7

Queue 2: Video Traffic CoS = 4,5

Queue 3: Best Effort (Transactional Data) CoS = 0,3

Queue 4: Background Traffic (Email) CoS = 1,2

Call acknowledgment carry out is a sort of QOS which boundary a array of video sessions to equivocate oversubscription of a priority reserve during a switches as good as routers. The work of a gatekeeper work monitors a array of video sessions as good as denies any one some-more sessions formed upon a bandwidth sourroundings of a queue. The priority reserve is configured with sufficient bandwidth for a specific array of sessions as good as any requests for one some-more sessions have been denied if which exceeds a reserve size.

4. Bandwidth

As mentioned, you do a opening comment of a tide network will brand where one some-more bandwidth is needed. The association WAN is a many usual source of problems with bandwidth. The superiority as good as low price of Metro Ethernet Gigabit circuits right away have it is a good event to muster it upon a association network.

Shaun Hummel is a writer of Network Planning as good as Design Guide as good as http://www.CiscoDesignBooks.com featuring Networking Books, eBooks, Certifications, Articles as good as Design Tools.

Copyright 2011 Shaun Hummel All Rights Reserved

 

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