Full Product Name, Model: TamoGraph Site Survey 2.0
Manufacturer’s URL: http://www.tamos.com/
List Price: $749 (Standard) or $999 (Pro)
Pros: Easy to use, flexible and fast, rich reports, modestly-priced
Cons: No active survey, no RF planner or spectrum integration
Before WLAN deployment, two tools can be handy: a predictive planner to recommend layout and a site survey for in-situ measurements. Given 802.11n’s multi-path propagation, some practitioners question whether extensive planning is worthwhile. But even for 11n, post-deployment surveys are essential to verify that installed WLANs meet and continue to satisfy each site’s unique requirements.
Enterprise site survey products start around $2,000 — in part due to features that SMBs may not need. Installers pressed for cash may want to consider TamoGraph Site Survey ($749) — a lean-and-mean passive survey tool. No, TamoGraph won’t integrate with RF planners, spectrum analyzers, or iPerf. But we found TamoGraph fast, flexible, intuitive, and easier on the wallet.
Getting started with TamoGraph
As a stand-alone product, TamoGraph requires little to get going. Just run setup on any Microsoft Windows XP, Vista, 7, Server 2003/2008 (32 or 64-bit) PC with at least 2GB of RAM and 20MB free. Size matters for on-the-go tools. But since TamoGraph doesn’t run on iOS or Android, we conducted most of this review on an eeePC netbook.
TamoGraph can run without live Wi-Fi — for example, to analyze surveys on a desktop with a big monitor. But to conduct a new survey, TamoGraph needs at least one compatible 802.11a/b/g/n adapter. This supported list is solid — especially for Windows 7 and Vista. We tested TamoGraph on XP with an AirPcap NX USB and on Windows 7 with an Atheros 9285 PCIe.
Adapter selection is crucial, because a slow/weak adapter yields too-conservative results, while a fast/sensitive adapter produces overly-optimistic surveys. Using adapter(s) representative of your own WLAN is a survey best practice. TamoGraph can use multiple adapters to scan N channels simultaneously, but those adapters must be of the same type. To survey with different adapters, walkabouts must be repeated, but TamoGraph can export and merge independently-measured results for consolidated analysis and reporting.
GPS-enabled outdoor surveys require a TamoGraph Pro license ($999) and an NMEA-compatible receiver. We paired Pro with a Holux Bluetooth GPS receiver. Like most survey tools, Pro cannot be paired with non-NMEA GPS navigators. However, we found that a Pro license is needed only to create GPS-based surveys; those results can be imported into Standard.
Creating surveys with TamoGraph
It took just fifteen minutes to install TamoGraph and complete a quick two-floor survey. We weren’t tempted to consult the well-illustrated guide until we drilled into analysis. Even then, TamoGraph left little to the imagination. While not bare-bones, TamoGraph is a what-you-see-is-what-you-get tool, with few hidden knobs or nested screens, relying mostly on mouse-over detail.
TamoGraph divvies the screen into three resizable panels: scanned APs (left), site floorplan or map (center), and project parameters (right). Upon launch, clicking “New Project” runs a wizard which prompts for name/description, environment type, channel list, and map image (below). Then calibrate the floorplan or map and optionally tweak project parameters before walking the site to record passive RF measurements.
As anyone who’s surveyed a site knows, the devil is in the details. Surveys are labor intensive; balky tools cause frustration and waste. To this end, TamoGraph offers a choice of three survey modes that can be used in combination to find APs heard at any site.
- Point-by-Point: With this traditional approach, the surveyor pauses at regular intervals to click on a floor plan and run a channel scan. Scanning 11 2.4 GHz channels at 250ms requires pausing just a few seconds. Increasing dwell time or scanning 5 GHz takes longer, while whittling channels or using multiple adapters can make a survey go faster. But unlike some pricier tools (e.g., AirMagnet Survey), TamoGraph cannot survey 4.9 GHz or incorporate non-Wi-Fi readings from a spectrum analyzer.
- Continuous: This mode requires less map-clicking and gathers more data, but requires the surveyor to walk at a consistent speed in straight paths, clicking only to change direction. TamoGraph distributes readings evenly between each pair of clicked points. As you might expect, we found that measurements obtained with this method were faster, but more often impacted by human error.
- GPS: This mode can fully automate outdoor surveys, which can be a huge time-saver. Following map calibration, the surveyor clicks on just one point, closes the laptop lid, and then walks or drives throughout the area. So long as the GPS continues to get a satellite fix, TamoGraph repeatedly scans the channel list until the stop button is pushed.
Each method has its strengths; fortunately, you don’t have to choose just one. We used continuous mode for larger indoor areas, point-by-point in tighter and more populous spaces, and GPS for exterior perimeter surveys and neighborhood “war drives.”
However, all three methods passively gather only layer two measurements. TamoGraph cannot actively associate to any AP to measure throughput or latency. If you need layer three data, either step up to an enterprise-class survey tool or take another walkabout with iPerf or WaveDeploy.
Calibration and accuracy
Ultimately, survey accuracy is critical. RF planners and integrated enterprise survey tools from vendors like Ekahau and Motorola can factor in building material attenuation. But a stand-alone survey tool like TamoGraph can only estimate RF propagation based upon specified environment: indoor or outdoor, with high, medium, or low attenuation.
This is done by selecting the most applicable environment, which TamoGraph associates with an adjustable “guess range” (e.g., 10 feet). During walkabouts, clicking any point produces a shaded circle of that diameter. For best results, walk the site until your entire map is shaded. Where doing so is impossible or impractical, TamoGraph offers an “extrapolate beyond guess range” option to fill gaps (available but not recommended).
Accurate results also depend on precise calibration. Calibrating imported floorplan images is easy: just draw a line of known length. However, calibrating maps is a bit trickier. TamoGraph can import saved map images or maps downloaded from OpenStreetMap, Bing, or MapPoint. To download a map, type an address, longitude/latitude, or use GPS-supplied current location. After zooming/panning to isolate the desired area, TamoGraph saves the map image for offline use.
At this point, at least 3 known (preferably distant) coordinates must be marked on the map image. One option: move to 3 locations and take live GPS readings. But our GPS surveys were faster and more reliable when we just typed coordinates copied from an on-line map service. Which begs the question: If TamoGraph can download on-line maps, why can’t it auto-calibrate those maps by downloading their coordinates too?
Given good environment selection, decent calibration, and accurate map-clicking, we found that rigorous walkabouts yielded fairly accurate results. Heatmaps from separate walkabouts of the same area were largely consistent; interior AP locations were often predicted within 10 feet. The same cannot be said for edge APs, but that’s a common limitation, caused by insufficient data for good triangulation.
In fact, the more we used TamoGraph, the better our results. That says more about proper technique than product, but learning to make best use of TamoGraph didn’t take long. One option we’d add: the ability to delete faulty measurement points. This would be especially welcome in continuous mode, where unmarked pauses can require discarding an entire path-walk. To minimize this, break continuous surveys into shorter segments to be combined for analysis. Breaking larger sites into smaller survey zones can also improve map-click accuracy.
Analyzing TamoGraph’s results
One TamoGraph project can include many floorplans or maps, each associated with several survey runs. These can be saved for later analysis on the same PC or exported for merged analysis on another (separately-licensed) PC. The latter is great for analyzing a large or geographically-distributed WLAN, or visually comparing old and new surveys of the same site.
TamoGraph analyzes selected survey runs for a single image. For example, we could analyze our first floor perimeter survey results or interior survey results or both at once. But unlike a planner such as RF3D, TamoGraph cannot correlate adjacent floor measurements; heatmaps are all 2D.
During a survey, the left panel displays live AP properties commonly observed by many stumblers: SSID, MAC address, vendor, channel, current signal strength (dBm), encryption type(s), max PHY rate (Mbps), and number of spatial streams. But during offline analysis, the left panel is used to select SSIDs, channels, and APs for analysis (below). APs below a configurable threshold can be eliminated, but this list would be even better if it could be searched or filtered.
After APs are selected, TamoGraph displays its analysis in the center panel. Given sufficient signal and data, TamoGraph can auto-place APs on the floorplan or map. Alternatively, you can drag APs to their actual location to improve analysis. The more data we collected, the better TamoGraph was at auto-placement – although it put one high-powered neighbor in the middle of our building. (In general, neighbor APs should be deselected to focus analysis on your own APs.)
TamoGraph then generates color-coded heatmaps, corresponding to selected “visualizations.”
- Signal Level (Coverage) Heatmap: Depicts measured/extrapolated signal strength. By default, TamoGraph considers anything above -60 dBm excellent; below -85 dBm marginal. But you can click on the status bar to change nearly any map’s range or color scheme.
- Signal to Noise (SNR) Heatmap: Quantifies the extent to which signal exceeds background noise. For example, if RF noise measured at a given point is -90 dBm and signal is -50 dBm, SNR is an excellent 40 dB. Low SNR can be caused by RF interferers. Some common interferers are easily guessed, but tough cases may require spectrum analysis.
- Signal to Interference (SIR) Heatmap: Quantifies the extent to which an AP’s signal exceeds co-channel interference generated by nearby Wi-Fi APs. TamoGraph offers two parameters to tweak this map: the minimum signal which defines each AP’s coverage (determines area of overlap) and average utilization (determines low SIR impact).
- AP Coverage Areas: Depicts the RF footprint of each selected AP, based on configurable minimum signal strength. This makes it easy to visualize overlap, although we found it helpful to select just a few APs at a time (e.g., by choosing one SSID for APs that beacon many SSIDs). TamoGraph can also display a count of the APs covering each area.
- Expected PHY Rate Map: Uses AP capabilities and SNR to estimate the PHY rate of the strongest AP in each mapped area. We found this map misleading because it assumes that AP and client capabilities are equal. In reality, clients are often less capable, reducing negotiated upstream/downstream PHY rates. Furthermore, survey adapter selection can artificially cap measured PHY rates far below an AP’s maximum.
- Frame Format and Channel Bandwidth Maps: Shows whether Non-HT, HT-Mixed, or HT-Greenfield frames and 20/40 MHz wide channels are used by the strongest AP in each mapped area. We found this useful to spot areas impacted by neighboring legacy APs.
Finally, the single-most insightful map produced by TamoGraph is called Requirements (below). This visualization highlights any mapped area that fails to meet project specs. Although we skipped right over this earlier, every project is actually created with default minimum requirements for signal, SNR, SIR, PHY rate, AP count, channel width, and frame format.
TamoGraph offers three predefined specs – basic, medium, and advanced – that can be customized and saved to reflect your site’s needs. For example, “advanced” requires redundant, high-throughput connectivity – any area with low PHY rate or less than two APs will be shaded to reflect this shortfall. The Requirements map is effectively a “roll up” of all other TamoGraph maps, which we found useful to spot problem areas to be investigated with other heatmaps.
Documenting TamoGraph’s results
We found TamoGraph useful as an interactive tool — for example, selecting different survey runs to spot changes, or choosing different visualizations to diagnose problem areas. But the end goal nearly any site survey is to produce a written report, documenting the site’s projected or current performance and coverage.
Despite its price, TamoGraph can produce very professional-looking customizable reports, at both summary and detail levels (below). In fact, TamoGraph reports were cleaner and more comprehensive than reports we have generated using some far more expensive tools. Just select the plans, survey runs, APs, and visualizations to be included (overall or per-AP).
As we compared TamoGraph to other planner, survey, and performance measurement tools, its closest competitor seems to be comparably-priced VisiWave. At one third the cost, TamoGraph lacks advanced features commonly offered by enterprise-class tools – most notably, planner and spectrum analyzer integration. If we could add just one (big) feature to TamoGraph, it would be active survey support – especially for 802.11n where SNR is not a great proxy for throughput.
But TamoGraph does much more than basic freeware utilities like Ekahau Heatmapper; it has an entirely different focus than a basic on-line planner (e.g., Aerohive) or a performance assessment tool (e.g., Ekahau Mobile Site Survey).
Instead, TamoGraph does a bloat-free, professional job of meeting the in-situ RF measurement needs of that under-served “in between” market. To learn more, try TamoGraph for yourself – the 30-day trial limits each survey to 5 minutes and won’t save results, but is otherwise fully-functional and is an easy way to see whether this tool meets your own needs.
