Long range RF Transmitter/Transceiver required (more than 200 meters indoors)

I recently received a project in which I have been asked to design a panic alarm system, which works without interference from any other source in an urban environment. The system basically comprises of a transmitter circuit on which the user presses a button in case of any emergency or distress and this signal is received at the receiver end, where a number of transmitter devices are being monitored.

I require an RF transceiver module (or an appropriate transmitter and receiver) for my project. The transmitter's range should be at least 200 meters indoors. Most of the transmitters or transceivers available commonly in the market only have a range of 90-100 meters indoors. I need more range at a reasonable cost, as the long range modules are either not readily available or highly complex to interface or very expensive.

I need help to find the most suitable transceiver module for this project. I would be very grateful if anyone could point me in the right direction as I personally have no experience with RF modules. I would also like to know where I can order them from. Do you know of any website which sells reliable electronic equipment, particularly RF modules?

Any help would be highly appreciated. Thank you very much.

Maximum range is related to max possible TX power.
Different countries have different regulations for how much power that is allowed in each frequency range.
If wearable unit => less available power and maybe less effective antenna.
Frequencies above 2 GHz gets more absorbed by indoor environment.
Low frequencies range requires bigger antenna for same radiation effectiveness.
A house with wooden walls absorbs much less signal then concrete walls. It can be a difference at a factor 10 or more.
Similar problem if you plan to cover several floors, with the difference that it is less numbers of doors and windows which can leak signals and a concrete floor is much thicker then a wall.
Knowing all these circumstances can be a good starting point.

RF useable frequency range without interference in urban environment, sure, if you can find an such environment free from computers, phones, electric motors and cars in the neighborhood.

Every antenna have some real weak directions and every building have some spots with low coverage at a specific frequency=> it is not possible to promise 100% coverage within 20 meter even if you use very powerful transmitters.

A common solution to improve likeliness for coverage is to use several overlapping base stations or slave relays.
Transmitters can also be acoustic. Both passive and active devices exist and hear able or high frequency not hear able. Receivers can be combined with existing network for burglar alarm/fire alarm /smoke detectors.

I know a similar project ordered by a fire department for a big building. The problem is that, nobody can guaranties a solid communication in a 200m indoor environment using relative low power transceivers.
So the chosen solution for this special application, was to use dedicated repeaters placed at decent distance one to each other. The cost was increased in concordance.

If you need an indoor panic alarm system, in any building you can install simple acoustical beepers or bells, and instead of RF I would suggest to utilize AC power lines over which you can transmit a 10 or 100 kHz set-off signal from a generator located anywhere . Coupling to AC power line can be done via 0.1 uF, 600 V capacitors to either wire, at transmit an receive side.
Using RF can cause or can be affected by interference; a simple on/off system like above can be built for a low cost and will work well even without AC power present ( the transmitter and receivers can operate on batteries).
There are also "wireless" door-bell extenders available on the market. Try using a higher transmit power, and use AC power line as a good antenna available throughout any building.

Thank you for your prompt replies everyone.

Actually when I was given this project, my first instinct was to use a GSM-based alarm system, which would easily solve the issues of coverage and range in both, indoor and outdoor environments, but I was informed that the problem with this approach is that most burglars use GSM jamming equipment to prevent any possible phone calls to the police. The problem with the hard-wired systems (using AC or telephone lines for communication) is that they can also similarly be compromised by simply cutting the power supply or the phone lines. I was specifically told to design a wireless solution to this problem using RF modules, although in my opinion this form of communication is also susceptible to frequency jamming attacks like the GSM.

The system would actually have most of the transmitter devices in very close vicinity to each other (well within a 100 meter radius). The only problem is the single receiver, which would be at least at a distance of 200 meters from these transmitters. I was thinking that if I used transceiver modules for my project instead of transmitters, interfaced each one with a micro controller, and then programmed these micro controllers in such a way so that they broadcast whatever signal they receive. This way if the panic button on any one of the devices is pressed, it would pass this info to all the other devices within its range and they would do the same until the signal reaches the receiver end. The signal being broadcast would contain the serial number of the device which was activated when the button was pressed and this information would be used at the receiver end to determine the where the distress signal came from. This approach would reduce the cost of using repeaters at multiple locations and basically would not require any new network or infrastructure (multiple base stations) to be set up. Can this approach, however, be implemented?

I think you must update a bit how normal security systems are built. Cutting wires is from the past or bad movies.
All wired professional burglar/fire alarm networks are wired in a such way that shortcut or cutting gives alarm status. In the most simple form is four wires used. Two for a parallel communication/power and two for a serial communication with a resistor in serial at each unit. Total current consumption and sling resistance is monitored at base station. Even cheap base stations for home use form 200$ have such functions. Wireless systems between relay stations are protected in a similar way. A jammer that continuously blocks an unit activates therefore an alarm.

A bit more professional systems, are also using semi random numbers in communication to ensure that all systems are active and not manipulated.
If a such system exist can it in most cases easy be extended to handle panic relay units and cost would be much less then building a new infrastructure that seems complicated and with a bit unpredictable function.
A system with multiple units, that in worst case moves around, and should be depending on that they can reach another unit within say 50 meter for transferring a alarm status is in best case a complement to an existing system coverage outdoor. Guarantee a such function indoor is a joke.
Opposite logic is more reliable, where all panic unit is continuously transmitting in time slots that everything is ok. For that can simple bluetooth units be used.
A unit that stops transmitting does then activate a alarm. So if a burglar is using a jammer, it will trigger a alarm.
Drawback with this logic is that the wireless part consumes power all the time and must periodically be recharged.
It requires very rigorous routines or else would it make whole system very unreliable due to a lot of false alarms because of units that becomes discharged or that someone leaves the protected area without unregister the alarm-button. It is a very basic factor in security systems that if a alarm is triggered, must it be for real, false alarms reduces reliability that next alarm is handled as a real alarm. (See bad movies again).
If a burglar is expected using a jammer had I built a jammer-sensor for that reason, even if it not disturbs existing alarm system. Then will an alarm be triggered before someone even had entered the the protected area.

Once in the time was a basic idea with bluetooth that is should dynamically be able to build wireless network to increase coverage range between two units. As there was to many security related problem with this was it dropped.
Whatever technical stuff a burglar is using, it is simple to make wired function very secure, the weak length is the wireless part.
A burglar that is using a jammer is the same as the burglar is saying "Here I am" if you is designing an alarm where this should be taken in account.

From your wishes and from quite qualified responses by others I can see that you are trying to build a better guarding system than those being used.
To overcome the thugs' thoughts, you can combine or update any existing alarm system, and thugs always invent how to overcome yours.
Isn't it easier to pay a couple of armed guards?