Wireless sensor network: Wireless RF circuit design

Hey Guys!

I am busy on a wireless sensor network(WSN) design project. I want to implement my system in Vineyards in South Africa.

This project has a lot of software in it so I am trying to get the hardware done as fast as possible. I ran into a slight bump today when my design examiner told me that my wireless data transfer cannot be done using a module( such as xbee, zigbee, wifly,etc). This is bad as I have already purchased a pricey Zigbit development kit, but now I have to design my own system capable of wireless transmission(1 way) from the roving sensor station to a base station.

I want to use RF in my design, I have yet to do a module at university where this is taught, so this is new territory for me, I am loving the challenge though.

I have researched quite extensively and found quite a few techniques, however quite a few of these are too complex. I wish to obtain a range of 1km minimum and have one way communication. 2 way communication could be an advanced spec. for my design though, which i don't mind implementing.

I just would like to know if you guys have any techniques that could help me.

Thanking you very much

Are you up to
- design your own RF chip
- build RF transceivers with commercially available chips, e.g. from TI, Hope RF or Slicon Labs
- design the RF circuit from discrete components?

1 km is beyond the easily available range of license-free small radio devices, what are the radio band and transmitter power constraints for your project?

What you mean with 1-way versus 2-way. Are you considering a network mostly comprised of transmitters?

I am up to all of the above mentioned tasks.

When i talk of 1-way transmission, I am referring to the fact that my rover station only needs to transmitt its telemetry data to the base station. I am considering, as a further specification, making transmission 2-way. I am still considering the application for 2-way that will best suit my project.

i want a radio band frequency of around 2.4ghz and am not too sure about the power constraint.

Why you can't use a module?
I would say designing your own RF chip would is out of scope, since it is very time and cost intensive.
The other two options from FvW sounds good, but require also a lot of work, especially when you are new to the RF topic. They could perhaps form an own project

For using high power at particular frequency you need a license. There are license free bands - such as the 2.4GHz - but you only allowed to use limited amount of power.
With the allowed power 1km is probably impossible to reach.