A strong communication network is now regarded as one of the most important infrastructure layouts for anyone to have.
Without communication, it would not be possible to remotely start/stop or monitor any processes.
According to the IEEE standard, the maximum recommended distance for a cable such as Unshielded Twisted Pair (UTP) is 100m. This poses a rather large concern for certain environments as much longer distances are required.
There are certainly ways around this, some options might include making use of Fiber Optic Cable which can run up to 100’s of Km’s. However it is not always practical to make use of fiber due to accessibility for cable routes. This leaves us with the option of looking at different Wireless solutions.
When looking at using wireless communication for a mission critical application it is important to ensure the wireless choice will give the security, distance, throughput and reliability you are looking for.
The easy, inexpensive wireless option is to make use of IEEE802.11a/b/g/n which does not require any licensing (However it is always recommended to make use of equipment that has local telecom authority approval, in South Africa this organization is ICASA – Independent Communication Authority for South Africa). When making use of IEEE802.11a/b/g/n equipment it is strongly recommended to ensure you are using the correct standard for your correct application. The IEEE802.11i option is also important as this adds to the level of security used on the wireless link.
The IEEE802.11i standard gives added security to your wireless system. As opposed to simply authenticating using the commonly known WEP (Wired Equivalent Privacy), which is fairly easy to penetrate from a wireless perspective since it is a shared medium, the IEEE802.11i adds stronger encryption, authentication and key management strategies to improve data and system security with integrity.
When using IEEE802.11/a/b/g/n, with keeping in mind licensing is not required, any civilian or person with or without malicious intent, would be able to use standard equipment to scan, snoop, unknowingly induce a duplicate IP address or wireless broadcast storms on your Wireless channel range, which in turn would lead to potentially harmful communication disruptions. Therefore this could be a good option if you have completed a site survey with a spectrum analyser and ensured there are not interfering signals that could deteriorate your wireless signal strength and that no breaching signals can penetrate your Access Points from the perimeter.
One of the shortfalls with IEEE802.11 Wireless standards is that distance is still a limiting factor. There are people who are already pushing this type of wireless reliably across a single 2-4Km Line of Site stretch (Line of Site indicates the two antenna’s are able to “see” each other without any obstacles in the way).
If you have a requirement for wireless to communicate past 2Km’s, then it might be more of a feasible solution to look at different WiMax options. WiMax is generally used for a large coverage, private, wide area network.
Worldwide Interoperability for Microwave Access (WiMax) is an IP based wireless broadband technology that is intended for large distances up to 15Km. This can be configured as a Point to Point, Point to MultiPoint or Repeater configurations, based on application requirements.
Certain frequencies in WiMax will require licensing. This is an additional cost, however by licensing your WiMax frequency this will give added confidence that you shouldn’t have any interfering signals disrupting your frequency around your area, therefore ensuring you will be the only one using your frequency and not sharing this airwave with other companies or applications and that in turn gives you more reliability of the link and ensuring throughput requirements are met.
When selecting a WiMax solution it is important to be specific on your requirements and the functionality you require. WiMax is defined by the IEEE802.16 standard and has since been enhanced to IEEE802.16e Wave 2 Certification.
The e in the standard represents additional security and functionality with ability to support the addition of an Access Service Network (ASN) communication gateway. The ASN Gateway will add the ability for mobile users to maintain a connection session while jumping between base stations. However the WiMax solution can run as a standalone solution without the ASN Gateway.
Wave 2, amended at the end of the standard, represents the development and standardization of using Multiple Input/Multiple Output (MIMO) Technology with WiMax. This added the ability to have WiMax links that can create and maintain connections over further distances and over Non Line of Site (NLOS) environments.
Most WiMax solutions typically comprise of a Base Station (This is the equivalent to an Access Point) and Customer Premises Equipment (CPE) or more commonly known as a subscriber unit (SU), (This is the equivalent of a client connecting to an access point). The CPE Base Station connection would be almost transparent to the end user.
One example for WiMax use is to connect a Field Device in a remote location connecting to a Subscriber Unit(SU). The SU would connect to a Base Station which in turn connects the rest of the network. Uplink is referred to as the connection speed in perspective from the CPE to the Base Station. Downlink would refer to the connection speed from the Base Station to the CPE.
Most WiMax vendors offer a ratio of 75% Downlink and 25% Uplink. This is a very good solution for a remote end user wanting to download information from their VPN Network to their office or downloading from the internet. However this does not necessarily cater for Automation and IP CCTV systems. If wanting to use this for Substation Automation making use of Generic Object Oriented Substation Event (GOOSE) messages a higher Uplink ratio would be required for the end devices to send their status update information as an example. The same principle for the IP Cameras, for a large wide area deployment CCTV Monitoring System, the IP camera would make use of the Uplink to send the camera feed to the server. If users wish to view the camera, they would connect to the server which would have a cable connection to the network. RuggedMax offers 3 static Ratio options for Uplink/Downlink ratios. Options of 75/25, 50/50 and 25/75 are available based on application requirements and is a nice example to understand how systems can be tailor configured to cater for specific application requirements.
There are two methods that cater for how WiMax integrates and work with IP/Ethernet networks:
IP Convergence Sublayer (IP CS) – In this mode the IP Header is carried over the system from the CPE to the Base Station but we can see from Diagram 1 the Ethernet header is not carried over the air by the system and thus non-IP traffic is not supported. For a private network wanting to make use of automation protocols, this type of isolation is not required and in many cases can prove to be a hinderence where Ethernet services are required such as certain industrial and utility based protocols.
Ethernet Convergence Mode (Ethernet CS) – The IP packet is sent from the CPE to the Base Station, as we can see from Diagram 2 the IP and Ethernet headers are maintained and the CPE/Base Station will rather encapsulate the entire Ethernet Frame and sends it using the 802.16e interface. When the packet arrives at the Base Station/CPE the 802.16e Header is removed from the associated hardware device and then the hardware forwards the frame to the appropriate network or CPE according to the MAC address.
Diagram 1 :
Diagram 2 :
Unfortunately WiMax is not yet as easy as an IEEE802.11 solution, that one can simply purchase of the shelf and install and configure according to requirements.
For any WiMax project there is a lengthy process that should be followed to ensure the end requirements are met specific to that application in terms of throughput, redundancy, overall reliability and network status update information.
The following Process flow is an example for gathering information for a project (All of the below processes make use of a WiMax feasibility Planning Tool):
Requirement Analysis
A Spectrum is required from the local Independent Communication Authority, once this is awarded the Frequency Band and Channel Bandwidth are required. In short a Spectrum allocation is made up from a Frequency Band (eg: 2.5-2.7GHz) and the channel Bandwidth is the difference in that frequency of the upper and lower frequencies (eg: 5,7,10 MHz)
Coverage Analysis
The Area Geographical information is a requirement. If there are mountainous regions, calculations need to be made in order to ensure there will be enough signal strength at the locations that are required. An example would include and be comprised of the following: Coverage Extent, Continuity, Depth, Probability (eg: 95%) objectives.
After the Coverage Objectives are complete the Site Information/Existing Towers and Site Connectivity information need to be acquired. This would be identifying the sites for the base stations and CPE’s and asking questions like: Are there any existing structures to install the Base Stations that will give us the coverage we require? If so, what are the GPS co-ordinates? If not what are strategic locations for the towers to be installed? The same would be required for the CPE locations. It would then be up to the customer to complete communications to the rest of the network, unless it is a long haul WiMax option, more details would then be required.
Capacity Analysis
Capacity and Traffic requirements from the customer are calculated and used to determine Uplink/Downlink throughput requirements based on the above collected information.
Path Profile
This is to determine if there is Line of Site (LoS) to all CPE’s from the Base Station coverage allocation. If not, Non Line of Site (NLoS) options are explored and calculated.
Interference Analysis
Calculations here are based on different scenario testing from surrounding areas.
Frequency Planning
This process is completed using a planning tool and inputting the above required information.
Only after the preceding processes have been completed can you determine feasibility and hardware requirements for your WiMax application. Once the information has been combined and calculated you can be certain of your investment into your new personal coverage wide area network in terms of security, reliability and throughput ensuring smoother running processes offering higher productivity and control.
Information supplied by :
Doron Kowensky,
H3iSquared
With thanks to Ruggedcom for assisting with information from standards committees.
For more information please contact:
Email : info@h3isquared.com
Web : www.h3isquared.com
Tel : (+27) 11 454 6025