In order to provide a context aware location based service to a mobile phone user, the first thingrnis to know the exact location and context of the user. To know the exact location of the user therernare different positioning techniques. Some of these techniques need support of Telecom providerrnand other methods require an embedded GPS. But the cost of most smart cell phone that has GPSrnis expensive and economically not affordable for most people in the country.rnTo overcome this problem we propose the context-aware LBS architecture that reads and processrnthe location and context information of a user using ordinary cell phones. The architecture isrncomposed of the client mobile device and the context aware LBS server. The client mobilerndevice end consists of components responsible for reading the location and context data from thernclient cell phone. The context aware LBS server side consists of components responsible forrnprocessing the location and context data that comes from client cell phone and make decisionsrnbased on different information stored in the server. The LBS system uses mathematical model ofrnlateration methods based on the signal strength and cell-ID received from telephone cell towerrnwhich all types of mobile phones can read.rnTo evaluate the validity of the proposed architecture, we developed a prototype that implementsrnthe core components of the proposed architecture. The implementation has been evaluated with arnsample services areas between localities in Addis Ababa named as Arat Kilo and Sidist Kilo.rnResults from the experiment show the proposed architecture is promising to provide a contextrnaware city guide services for users including those using ordinary (non-smart) phones withoutrnGPS.rnKeywordsrnLocation Based Service, Context-Aware, Trilateration, Cell-ID, Received Signal StrengthrnIndication