Beyond the Box: Why AP Placement is Critical

Many people believe that the secret to great Wi-Fi is simply buying the most powerful, expensive router on the market. While a high-quality device is important, it is only half the story. The truth is that the performance of any wireless network is just as dependent on where the access point is placed as it is on its technical specifications. An Access Point (AP) is the heart of your wireless network, broadcasting radio waves that carry your data. Just like a lightbulb, its ability to illuminate a space effectively depends entirely on its location. Placing the most powerful lightbulb in a closed closet will not light up your living room. Similarly, placing a high-end router in a basement corner, surrounded by concrete walls and metal pipes, will result in poor performance and frustrating dead zones throughout your home.

Proper Access Point design and placement is a science that blends an understanding of radio wave physics with the practical realities of a physical environment. It is the process of strategically planning the location, configuration, and number of APs to create a seamless, high-performance wireless network that meets the specific needs of its users. This process revolves around achieving a delicate balance between three core pillars: Coverage, Capacity, and Channel Planning. Getting this balance right is the difference between a network that merely works and one that works exceptionally well.

Pillar 1: Coverage Planning - Eliminating Dead Zones

The most fundamental goal of AP design is to ensure adequate signal coverage in all the areas where you need to use your wireless devices. A Wi-Fi signal is not magic; it is a physical radio wave that weakens with distance and is blocked by physical objects.

The Art of Placing a Single Access Point

For a small apartment or a single-story home, a single, well-placed router can often suffice. The key is to treat it like the sun in a small solar system.

• Central Location: The ideal placement is in a central location, as close to the middle of your home as possible. This allows the signal to radiate outwards more or less evenly in all directions, minimizing the distance it has to travel to reach the farthest corners.
• Elevation and Open Space: Place the AP as high up as is practical, for example on a high shelf or mounted on a wall. Radio waves travel best through open air. Placing it on the floor or tucking it behind a couch will cause the signal to be immediately absorbed and blocked by furniture.
• Avoid Obstacles and Interference: Keep the router away from large physical obstructions, especially those made of signal-blocking materials. Common household materials have a dramatic effect on Wi-Fi signals:
  • Metal and Concrete: These are the worst offenders. They block signals almost completely. Avoid placing APs near large metal appliances like refrigerators or in basements with thick concrete walls.
  • Brick and Plaster: These materials also cause significant signal loss (attenuation).
  • Glass and Wood: These are less obstructive, but still weaken the signal. Even a standard window can reduce signal strength.

  Equally important is to avoid sources of RF interference. The 2.4 GHz band is particularly susceptible to noise from microwave ovens, older cordless phones, baby monitors, and Bluetooth devices.

Professional Coverage Planning: The Site Survey

In larger or more complex environments like multi-story homes, offices, or warehouses, a single AP is rarely sufficient. Professional network design requires a more rigorous approach known as a site survey. This is a process of mapping out the wireless environment to determine the optimal number and placement of APs.

• Predictive Site Survey: This is the first step. Using specialized software (like Ekahau or NetAlly), a network designer imports the floor plans of the building. They then digitally place virtual walls, doors, and furniture, assigning them the correct material properties (e.g., concrete, drywall, glass). The software can then simulate how radio waves from virtual APs will propagate, creating a "heatmap" that predicts the signal strength throughout the entire area. This allows for initial planning and estimating the number of APs needed without any physical hardware.
• On-site (Physical) Site Survey: The predictive model must then be validated in the real world. This is often done using a method called "AP-on-a-stick". A single access point, powered by a battery pack and mounted on a portable tripod, is placed in a proposed location from the predictive survey. The designer then walks around the intended coverage area with a measurement device (like a specialized Wi-Fi scanner or a laptop running survey software) to take real-world measurements of signal quality. This process is repeated for each proposed AP location to verify and fine-tune the design.

During a survey, two key metrics are measured to define coverage quality:

1. RSSI (Received Signal Strength Indicator): This is a measurement of how much power is present in a received radio signal. It is measured in dBm. Because the power is very small, the value is always negative. A number closer to zero is better. A general guideline for a good, usable signal suitable for voice and data applications is an RSSI of $-67$ dBm or better (e.g., $-60$ dBm is stronger than $-70$ dBm).
2. SNR (Signal-to-Noise Ratio): This metric is arguably more important than RSSI. It measures the strength of the desired Wi-Fi signal compared to the level of background radio noise (interference). It is measured in decibels (dB), and a higher number is always better. A high RSSI is useless if the noise level is also high. For a reliable, high-performance data connection, an SNR of $25$ dB or higher is generally required.

Pillar 2: Capacity Planning - Handling the Load

Having a strong signal everywhere is a great start, but it does not guarantee good performance. The second pillar of AP design is capacity planning. This involves understanding how many devices will connect to the network and what they will be doing, and then deploying enough APs to handle that load without getting overwhelmed.

A single AP can only talk to a limited number of devices at once and has a finite amount of total throughput it can provide. Adding more and more clients to a single AP will eventually cause it to become a bottleneck, resulting in slow speeds for everyone, even if they have a perfect signal.

Factors in Capacity Planning

• User and Device Density: The first step is to estimate how many devices will be active in a given area. A high-density environment like a lecture hall, conference room, or stadium, where hundreds of devices are concentrated in a small space, requires a very different design from a low-density environment like a typical home.
• Application Requirements: Not all network traffic is created equal. Different applications have vastly different bandwidth and latency needs. A good design must account for the types of applications that will be used.

  Application Type	Bandwidth Need	Latency Sensitivity	Examples
  Basic Data	Low	Low	Email, web browsing, IoT sensors
  Voice over Wi-Fi (VoWiFi)	Low	Very High	Voice calls
  Video Streaming	High to Very High	Moderate	Netflix 4K/8K, YouTube
  Real-Time Interactive	High	Very High	Online gaming, video conferencing, AR/VR

To ensure adequate capacity, a designer will often create a "capacity-based design" where the number of APs is determined not just by the need for signal coverage, but by the need to support a certain number of users or a certain level of throughput per area. For example, if a lecture hall will hold $200$ students, and it is assumed a single AP can comfortably handle about $40$ active students, the design would call for at least $200 / 40 = 5$ APs in that room, even if one or two APs could provide basic signal coverage.

Pillar 3: Channel Planning - Avoiding Self-Interference

Once you have determined where to place your APs for coverage and capacity, there is a final, critical step: channel planning. The radio spectrum used by Wi-Fi is a shared, limited resource. If multiple APs in your network are trying to "talk" on the same channel at the same time, they will interfere with each other, just like two radio stations broadcasting on the same frequency. This is known as Co-Channel Interference (CCI), and it is a major source of poor performance in multi-AP networks.

The 2.4 GHz Challenge

Channel planning is most challenging in the 2.4 GHz band because of its limited spectrum. This band is divided into 11 or 13 channels (depending on the region), but most of these channels overlap with their neighbors. Using overlapping channels is even worse than using the same channel, as it causes Adjacent Channel Interference (ACI). In North America and many other parts of the world, there are only three channels in the 2.4 GHz band that do not overlap at all: channels 1, 6, and 11.

A proper channel plan for a multi-AP deployment in the 2.4 GHz band involves creating a cellular-like pattern, assigning channels 1, 6, and 11 to adjacent APs in a way that maximizes the physical distance between any two APs operating on the same channel. This minimizes their chances of hearing each other and reduces co-channel interference.

The 5 GHz and 6 GHz Advantage

Channel planning is significantly easier in the 5 GHz and 6 GHz bands. These bands are much wider and offer a large number of non-overlapping channels. For example, the 5 GHz band has over 20 channels, and the 6 GHz band has nearly 60 non-overlapping 20 MHz channels. This abundance of space means that in most deployments, every AP can be assigned its own unique, non-overlapping channel, completely eliminating both CCI and ACI between the APs in your own network. This is one of the primary reasons why the 5 GHz and 6 GHz bands offer superior performance to the 2.4 GHz band.

Power Levels: Turning Down the Volume

A common misconception is that APs should always be set to their maximum transmit power. While this seems intuitive for maximizing range, it is often detrimental in a multi-AP environment. If APs are "shouting" as loudly as possible, their coverage cells will overlap extensively, creating massive amounts of co-channel interference and confusing client devices.

A key part of professional network design is tuning the transmit power of the APs. The goal is to lower the power just enough to create well-defined coverage cells that provide the intended signal strength at their edge, with minimal overlap with the cells of neighboring APs on the same channel. This reduces CCI and encourages client devices to roam to a closer, better-performing AP in a more timely manner. It is a balancing act: too much power creates interference, while too little power creates coverage gaps. Finding the right power level is a critical final step in optimizing a wireless network.