Wireless Networks You Can Count On!
With wireless LANs, employees can access corporate networks without looking for a place to plug in and gain true mobility. Network managers can easily set up or expand networks without installing or moving wires saving about $200 per network jack.
InterNetworking Link offers consulting(selection, installation and optimization of client devices), pre-installation site surveys(manual, adaptive, predictive modeling), maintenance and on-site support to help you build or expand your computer network. All our technicians have either a leading vendor training or a vendor neutral certification.
Effective Site Survey To Establish:
- Your users needs
- The RF behavior
- Discover interference
- Layer 2 Retransmissions
- Spectrum analysis
- Hardware selection and placement
- Integration with existing networks and systems
- Nature or Changes in your environment
- Integration with sensor networks, PANs or RFIDs(identification systems)
802.11 Maintenance Services
- Applying firmware upgrade or substituting with better open firmware when available
- Updating radio equipments
- Optimizing the WLAN to support voice and video traffic
- Updating client drivers
- Optimizing transmission power rates
- Verifying use of proper antenna types
- Applying Encryption standards
- Updating clients and servers(patches, service packs, hot-fixes)
- Attack surface reduction
- Vulnerability assessment
- Hunting and removing rogue devices
- Penetration testing
- Weatherproofing of outdoor equipment with NEMA enclosure units
- RF beam correction and Antenna stabilization
- Bridge links realignment and optimization
Our 802.11 Troubleshooting Services
Our troubleshooting services aim at detecting and resolving issues adversely affecting your WLAN performance and these include:
Layer 2 Retransmissions are the mortal enemy of WLAN performance. They increase overhead, decrease throughput or affect the timely and consistent delivery of time-sensitive applications such as voice and video. With protocol analyzers we track layer 2 retry statistics for the entire WLAN and for each AP and client station(ideal rates for packet loss are less than 10% for data traffic and no greater than 2 to 5% for time-sensitive applications).
No connectivity due to incompatible radios or encryption schemes, RF interference caused by neighboring devices, faulty configurations, etc.
Intermittent connections caused by hidden node, near/far problems or disabled RTS/CTS. The half-duplex nature of 802.11 usually prevents most near/far occurrences. But, the hidden node can drive layer 2 retransmission rates above 15 to 20 % or higher causing degradation, latency and jitter. We troubleshoot with a protocol analyzer. If it indicates a higher retransmission rate for the MAC address of a particular station compared to other STAs, chances are a hidden node has been found. Further troubleshooting includes inspecting your environment for obstructions that were missed or were not present when your site survey was performed. We also inspect radio locations to see if they were placed or relocated to a bad place. When appropriate, we disable the data rates of 1 and 2 Mbps on a/b APs for capacity purposes
Decreased throughput caused by over-utilization of network or by poor configuration that results in management overhead consuming more than 50% of bandwidth
Distributed antenna systems(long coaxial cable with multiple antenna elements and each antenna having its own coverage area): Although very cost effective, these systems are notorious for causing the hidden node problem. Another way we diagnose this problem is to enable RTS/CTS and use a protocol analyzer equipped with hidden node alarms. By lowering the threshold to a level appropriate(500 bytes for standard traffic or as low as 30 bytes for terminal emulation traffic) to the type of traffic being used, we can trigger the hidden node alarms. Once confirmed, the best solution is to add more APs, especially when moving the hidden nodes is not an option
Weak signal strength. If your physical environment has changed, we can reposition your APs or client devices, modify output power settings, use external range extender antennas or use signal boosters
Inter-symbol interference(ISI) caused by the multi-path phenomenon: Delay spread introduced by multipath can cause problems with signal demodulation and result in data corruption and further layer 2 retries. Where our multipath analysis troubleshooting tool(Berkeley Varitronics Systems) visualizes occurences of multipath and the delay spread(usually indoors in long corridors and anywhere metal is located), we try to compensate with antenna diversity using unidirectional patch antennas. Since non OFDM legacy equipments are less resilient to multipath, we also have the option of upgrading/replacing all radios from DSSS to OFDM
Latency and jitter problems for time-sensitive applications. We identify and remove possible causes of increased overhead and decreased throughput.
RF interference: Our spectrum analyzers allow us to detect narrowband, wide-band and all-band interference. We can determine affected channels and design a channel reuse plan in case of the interfering narrowband signal or locate and remove the wide-band jammers that create a DoS. To eliminate all-band interference, we locate the interfering frequency-hopping transmitters(cordless phones, microwave ovens, video cameras, bluetooth, HomeRF, etc.) and update them with newer devices utilizing adaptive mechanisms to avoid interfering with your 802.11 WLAN
Adjacent Cell Interference: 802.11-2007 standard requires 20 MHz of separation between the center frequencies of OFDM(All 23 channels can be used in the 5 GHz UNII bands since they are non-overlapping) channels and 25 MHz of separation between the center frequencies of HR-DSSS and ERP-OFDM channels(no more than 3 channels can be used with 5 channels of separation in the 2.4 GHz ISM band) in order for them to be considered non-overlapping. Poor channel reuse design can therefore result in overlapping coverage cells with overlapping frequencies. The transmitted frames will become corrupted, the receivers will not send ACKs, and layer 2 transmissions will significantly increase.
Low SNR: If the amplitude of the noise floor is too close to that of the received signal, data corruption will occur and result in layer 2 retries. An SNR of 25 dB or greater is considered a minimum for voice WLANs and a SNR of 18 is the recommended minimum for data WLANs
Mismatched Power Settings: If the client’s signal drops below the sensitivity threshold of the AP’s radio, the client’s ACK frames will not be heard and this will result into layer 2 retransmissions and problems with VoWiFi phones. Our solution ensures that all clients(under a WLAN controller or not) transmit power settings match that of the AP or that the AP power be set to no more than the power of the lowest powered STA. 802.11k makes it possible for an AP to inform clients to use TPC capabilities to change their transmit amplitude dynamically to match the AP’s power
APs at full power: The best solution to increase the range of an AP or that of a STA is to increase the antenna gain rather than the power of the AP. Antenna reciprocity will amplify both the transmitted and received signal
Co-channel interference: Unless using a SCA solution, it is an improper channel reuse design to configure multiple APs on the same channel causing unnecessary medium contention overhead/defer transmissions. Only one radio can transmit on the same channel at any given time(channel cooperation). Radios on different channels can transmit at the same time. Co-channel interference is a less serious problem than adjacent cell interference
Oversized Coverage Cells: AP transmitting at full power not only cause some of the problems described above(hidden node, near/far issue, co-channel interference due to bleed-over transmissions) but also affect capacity needs. The more STAs on an AP, the lower the throughput. To troubleshoot capacity issues, we use cell sizing and AP colocation in a MCA environment. APs are physically separated from each other by at least 15 feet(5 m) to prevent possible interference by the sideband signals that the APs generate.
Improper Channel Reuse: To avoid co-channel and adjacent cell interference, a proper channel reuse design is necessary. This architecture is also called MCA. The more channels, the better the reuse pattern. That is why channel reuse design is much easier in the 5 GHz. Our troubleshooting entails the following. Any adjacent coverage cells in the 5 GHz must use a frequency that is at least two channels apart and there must be at least two cells of coverage space distance between any two APs transmitting on the same channel. Finally, the coverage cells of each AP should not extend beyond more than one floor above and below the floor on which the AP is mounted.
Is Wireless Secure?
On June 24th, 2004 the 802.11i draft standard was ratified by the IEEE to provide security standards to the 802.11 Wi-Fi worlds.
This new standard replaced the now proven weak WEP. The Wi-Fi Alliance refers to it as WPA2. It is now possible to have a secure wireless network.
Wireless ROI
- Easy Setup, Reduced Hardware, Reduced Costs
- Reduced space for equipment and cabling
- Convenience & Efficiency gain because of improved and easy mobility
- Improved productivity and service due to continuous access and availability throughout the facility
- Adds simplicity, flexibility, scalability
- Rapid installation, low cost creation of VLANs
Key Deployments
- Network Extension to remote, difficult or expensive areas
- Corporate Data Access and End-User Mobility(warehousing, manufacturing, hospitals, clinics, law-enforcement, etc) due to mobile network access
- Building-to-building connectivity – Bridging up to 24 miles
- Mobile Computing(PDAs, Tablet PCs, other handheld devices)
- Mobile/temporary Offices/classrooms during construction, disaster, military maneuver, first-reponders
- wVoIP or VoWLAN or VoWiFi
- Flexible Classroom layout design and easy networking
- SOHO easy networking and mobile internet access
- Last Mile Data Delivery(WISP)
- Real-Time Location System(RTLS) for tracking and inventory control(802.11 RFID tags)
- Public Network Access(Hotspots, transportation & municipal networks)
- Metropolitan wireless networking with WiMAX
- Fixed Mobile Convergence(FMC): WVOIP, Cellular and PSTN seamless switching and roaming in a single device using a single number and always favoring the least costly network available – 802.11u(Wireless Interworking External Networks)
