In the world of wireless design, terminology matters – especially when it affects cost, project timelines, and client expectations. A common misconception is that an AP-on-a-Stick (APoS) survey is a type of predictive survey. Let’s clear that up once and for all.
What is a Predictive Design or Model?
A predictive design/model is a design or modeling exercise done before any physical site survey. Using specialized software (such as Ekahau or iBwave), floor plans are imported, walls and obstacles are modeled, and AP placements are simulated based on environmental characteristics, required capacity, and coverage goals.
Key aspects of predictive surveys:
- Virtual simulation only
- Uses wall attenuation values and materials to predict signal propagation
- No physical AP installation required
- Fast turnaround for design proposals
- Ideal for new constructions or greenfield deployments
What is an AP-on-a-Stick (APoS) Survey?
An APoS survey involves temporarily mounting an access point on a tripod (the “stick”) and physically testing signal propagation at planned locations. The surveyor walks the environment with the AP transmitting, measuring actual signal strength and performance metrics.
Key aspects of APoS surveys:
- Physical on-site survey with live AP
- Validates predictive designs with real-world measurements
- Used when accuracy is critical (e.g. high-density or challenging RF environments)
- Time-consuming, requires site access and equipment setup
- Often done after predictive to confirm or adjust design
Why is APoS NOT a Predictive Survey?
- Different Design Phases
- Predictive surveys occur in the planning/design stage.
- APoS surveys occur in the validation stage (pre-deployment or post-predictive).
- Physical vs Virtual
- Predictive relies purely on software modeling.
- APoS uses physical APs broadcasting in the real environment.
- Purpose and Cost
- Predictive surveys are fast and lower-cost, providing an initial design.
- APoS surveys are labor-intensive, often used to validate or fine-tune the predictive design with real RF data.
- Required Equipment
- Predictive: Laptop and design software.
- APoS: Laptop, design software, battery packs, tripod, mounting kits, and live AP hardware.
Why This Misunderstanding Matters
Many clients believe APoS and predictive surveys are interchangeable. This leads to scope creep, inaccurate budgeting, and incorrect expectations on survey deliverables.
As wireless engineers, it’s critical to:
- Educate clients on these differences upfront.
- Clearly define survey types and deliverables in proposals.
- Use the appropriate survey type to meet technical requirements without unnecessary time or cost.
Final Thoughts
AP-on-a-Stick surveys and predictive surveys are both essential tools in the wireless engineer’s toolkit. However, they serve different purposes at different stages. Confusing them can lead to design flaws or wasted resources. Use predictive surveys for efficient, software-based planning and APoS surveys for real-world validation where accuracy is paramount.
A detailed blog post can be found here