Problem:

1. Communication needs to exist between the lab and a remote location at the surface.

1. Data rate needs to allow for a normal phone communication, and a decent internet connection, that would be used mostly for text transmission and applications that do not require a very big rate.
2. The range of emission has to be sufficient to reach a satellite.
3. Our system has to be self-sustained and completely independent. We cannot rely on Belizian transmitters and emitters.
4. We need to take into consideration cost, power supply, installation costs.

1. Need to have a gateway on the surface to transmit the information to remote locations.
2. Possible options to communicate with the gateway include fiber optic cable, Ethernet cable, and normal wire. (data rate 20-30 kb/s)
   1. Ethernet cable is expensive and considering our bandwidth, it offers no advantage over the fiber optic cable, which is less expensive.
   2. Normal wire wouldn’t be able to support our data rate.
   3. Fiber optic cable offers flexibility, can support our data rate, and is less expensive than Ethernet.
3. Gateway options include direct cable connection to the coast, digital emitter, and high frequency emitter.
   1. The cable connection is expensive, and can be easily damaged by boats.
   2. The emission of digital signals requires too much power.
   3. High frequency ground waves give the necessary range to reach a satellite, and they support enough data rate. Frequency range: 15-100 Mhz. Size and weight are reasonable.
4. Location. Two options were considered, a floating gateway, or a gateway fixed on the border of the blue hole.
   1. The floating option is not esthetically appealing (!), and it would cause a P.R. problem. The antenna is more likely to collapse.
   2. An on-land option is more stable and reliable.

Problem:

1. Communication needs to exist between divers, the base station and other divers.

2. Objects need to be located.

Requirements:

1. Communication

   1. Bit-rate needs to allow for one way speech. A typical phone line has a bit-rate of 14.4 kbits/s. Since a telephone line provides a high quality two-way conversation, 10 kbits/s will be sufficient for our needs.

   2. Regardless of the divers position in the upper part of the blue hole (depth<60m?) they will be able to communicate with others. The area covered by the communications system will be inside the reef outside the blue hole. This area is a circle with a 1000m diameter.

   3. All logistics need to be accounted for, including power, construction, cost, etc...

2. Objects need to be located at all times.

   1. Even in the event of a total systems failure

Solution:

1. Communication

   1. Possible protocols include acoustics, electromagnetic radiation, cables, and hand signals.

      1. Hand signals will not be able to transmit enough data to the involved parties

      2. Cables will restrict the diver's movement and range and are therefore undesirable

      3. Electromagnetic radiation does not travel far enough in water to be useful

      4. Acoustics has both the range and the bit-rate required

   2. Acoustics have varying ranges and data rates based upon the frequency of the transmission. Typical acoustic systems have frequencies between 3kHz to 50kHz. The higher frequencies have a higher bit-rate but a shorter range then lower frequencies. The optimal frequency to meet our bit-rate and range requirements is 32 kHz. This will allow communication greater or equal to 10 kbits/s and will have a range of at least 300m.

   3. With a range of 300m, relays will be necessary to completely cover the required area. The exact set-up of these relays will be discussed at a later time, because the set-up affects other systems that are still being designed.

   4. Regardless of the relay's positions, they all have to be connected and powered. Exact wiring diagrams are dependent on the relay location, but the cables connecting them will be co-axial cables. Along side the co-axial cable will run a power line. These cables also connect back to the base.

   5. The cost of this system still needs to be determined. The relays have not yet been defined and a large percentage of the cost is dependent on the relays.

2. Location

   1. In order to be located, the diver or object, will carry a small device that will emit a signal. This signal will be received by various relays throughout the blue hole. Triangulation based on the time delay of the received signal will allow give the objects location.

   2. The emitted signal does not have to carry much information. Therefore, the frequency can be very low. 3 kHz will be the frequency of the emitted signal.

   3. The relays that receive the signal will be packaged together with the relays used for diver communicaion. In order to accurately determine an object's position there must be four relays and there has to be at least one relays with a different x coordinate then then other three, another with a different y, and another with a different z. These requirements will help shape the location of the relays.

   4. In the worst case scenario, such as an injured diver is lost and the communications system has completely failed, there needs to be some way of locating the diver.

      1. The divers shall be equipped with homing devices that will emit signals at multiple frequencies, such that another diver could detect these signals and determine his/her location.

3. What next

   1. Location of relays based on the following requirements

      1. acoustic range <= 300m

      2. 3d triangulation must be possible

      3. No holes throughout the blue hole

      4. boats or robots may be used to temporarily strengthen signal in a certain area

   2. Cost Analysis

   3. Power Requirements