Multi-Link’s ZipLink Series of Wireless Ethernet Extenders offers several options with regard to Ethernet bandwidth. Selecting the right ZipLink model for remote IP video surveillance applications is obviously an important consideration. There are many factors that need to be taken into account so that an accurate measurement of bandwidth can be determined for current and future needs. Primary factors consist of IP video camera settings, number of IP video cameras on the network, and additional network traffic.
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As a frame of reference, the following chart shows the ZipLink model #’s and corresponding available wireless Ethernet bandwidth sent from the remote site to the main site.
|ZipLink 1 & 2||ZipLink-E||ZipLink-X200|
|12 Mbps (1 Mile)
||40 Mbps (1 Mi.)
||200 Mbps (3 Mi.)
How IP Video Camera Settings Affect Ethernet Bandwidth
The IP video camera settings that you can control that affect bandwidth usage are common across a wide variety of IP camera models and manufacturers. However, the default values of these settings tend to vary between models, but can be tweaked to optimize video quality and bandwidth. Some of these settings include:
- Video CODEC (Compression)
- Streaming Mode
- Frame Rate
- Video Quality
NOTE: Other settings like “Hours of motion” and “Days of Storage/camera” are a function of storage capacity — important, but not in our scope of discussion.
Without getting into a lengthy lecture on IP Video Surveillance 101, here are some helpful notes to use as a rule of thumb with regard to determining network bandwidth requirements:
Video CODEC: A video codec is a device or software that enables compression or decompression of digital video; the format of the compressed data adheres to a video compression specification. Compression (aka Quantization) is a major factor in IP video quality and network bandwidth usage! Between the most popular compression standards, MJPEG/MJPEG-4 and H.264, the H.264 format is the most widely used in the security industry. With IP video cameras, the compression is done inside the camera before it is sent along to the server. All things being equal, a setting change from MJPEG to H.264 can reduce network bandwidth usage by approx. 80% — a considerable reduction when multiple IP video cameras are deployed.
Streaming Mode: Constant Bit Rate (CBR) or Variable Bit Rate (VBR) are the options. The CBR mode streams at a constant, unchanging rate defined by the administrator and is useful when scene motion is always stable and bandwidth is limited. Conversely, the VBR allows for variations (increases) in the bit rate due to increased motion episodes. Access to higher bandwidth is required for this mode, but it minimizes the risk of losing valuable data packets leading to blurry images.
Frame Rate: When you watch your favorite TV show, you are looking at a “full” frame rate of 30 frames per second. Most IP video cameras can stream up to this rate. However, this would not be feasible for IP surveillance applications due to higher bandwidth and storage needs. In fact, a far more common setting would be in the range of 6fps up to 20fps, with 10fps as a happy medium. Good lighting also plays a role in the fps setting needed. Better lighting should equate to lower frames per second needed.
Resolution: How much does increasing pixel count from 2 MP to 4 MP affect bandwidth? Answer: It depends. Mostly on the make and model of the IP video camera. There is no hard and fast arithmetic formula that will give a reliable answer. Increasing pixel count by 100% may result in a increase of anywhere from 50% up to 200% more bandwidth needed.
Each of these variables can significantly affect the outcome of the video quality and small tweaks can have a great impact. The good news? There are a number of free and proprietary bandwidth calculators that are available online that can provide a reliable usage estimate for IP surveillance applications. These tools can also provide storage requirements as well.
How to Test Ethernet Bandwidth Usage When Adding IP Video Cameras
If you have your IP video cameras on hand and are ready to bench test for bandwidth usage in real time, you will need a network bandwidth measurement tool. Fortunately, your PC has one at the ready–the tried and true “Windows Task Manager”. Just hit CTRL-ALT-DEL and select the “Networking” tab. At the bottom of the usage graph (Fig.1) you can see available link speed and the associated utilization as a percentage.
As you add your cameras one by one, you can get immediate feedback on bandwidth usage and adjust each camera’s settings accordingly to optimize your network. While IP video cameras have software that reveal data usage on an individual basis, it is necessary to employ a network bandwidth tool to see how utilization is impacted across a multiple camera network.
At this point, it is important to realize that other factors in a real world deployment will come into play. Consider what each camera’s scene complexity will be—dynamic or static? Will it be a busy parking lot, or an indoor hallway with minimal traffic? Some complex scenes may require 3x times the bandwidth of a simpler one—a big difference!
Also be aware of scene changes over the course of a 24-hour day. Outdoor low light and night scenes will need more bandwidth–up to 5 times– than the other hours of day. A constant, well-lit area such as a lobby area should have lower usage spikes.
Always Factor in Other Network Traffic with Your IP Video Application
Now that you have done your testing & tweaking to estimate the bandwidth that the IP video cameras will need, another factor should be considered before you decide which ZipLink model will be right for your job. Namely, what other devices will be sharing the network resources at the remote site?
Basic file-sharing, internet browsing, and Voice over IP connectivity are typical uses for in a local area network scenario and will compete for available network bandwidth. The previous network feedback exercise can be repeated for each network device used at the remote site. VoIP calls by nature are not bandwidth intensive. An average VoIP call will be only 12Kbps in size, so an average size VoIP system will marginally affect available bandwidth.
With all network traffic accounted for— IP video cameras and all— you should aim to use no more than 75-80% of the available network bandwidth. For example, if you require 30 Mbps of total bandwidth from the remote site, the ZipLink-E with 40 Mbps of Ethernet bandwidth should accommodate your application. However, to provide for future network demands, the ZipLink-Xtreme 200 Mbps might be the better choice.
In Fig. 2 below, the ZipLink-E is providing 40 Mbps of wireless bandwidth for an IP Video surveillance application to a remote guardhouse within one mile of the master site.
The ZipLink-E is supporting 5 IP video cameras, a single VoIP connection, and internet access. Settings for each camera is: H.264 / 1080P HD resolution / 10fps / with high video quality for an average bandwidth of 4 Mbps/each (20Mbps total). VoIP bandwidth usage is nominal and assuming 10 Mbps will be enough for internet access, 10 Mbps of ethernet bandwidth is still unused. This is right at the maximum network usage recommended (75%).
Even though a ZipLink System can be set up and running in a couple of hours with no radio experience, it would be advisable to consider future network demands at the remote site before deployment! The ZipLink-Xtreme/200 (200Mbps) models could be better options for the above application if additional network assets are deployed down the road.
ZipLink ships as a complete working system:
- MASTER and REMOTE end radios; Pre-configured as working pair
- 2 x power adapters (POE injectors for ZipLink-E and Xtreme models)
- 2 x 100 ft. of outdoor Cat 3 cable (Cat 5e for ZipLink-E and Xtreme models)
- 2 x wall pole mount and brackets & all necessary screws, nuts, lock washers
For more information on IP video surveillance applications, contact a security industry professional. For questions on the ZipLink Series, call us @ 1-800-535-4651 or email: firstname.lastname@example.org.
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