Content caching method for satellite terrestrial integrated network with differentiated interest and access mode

A content caching method for a satellite terrestrial integrated network with differentiated interests and access modes, comprising:

• step (1), collecting user proportion information, content popularity distribution information, cache capacity information, and link delay information in the satellite terrestrial integrated network, wherein the satellite terrestrial integrated network comprises base stations, a satellite, base station access users, satellite access users, a ground station, and a cloud server;
• and a cover area of the satellite terrestrial integrated network is divided into multiple regions, and different regions have different local content popularity distributions;
• wherein the user proportion information comprises proportion information of the base station access users and the satellite access users in the satellite terrestrial integrated network, and proportion information of users in different regions covered by the satellite terrestrial integrated network;
• the content popularity distribution information is local content popularity distribution information of different regions covered by the satellite terrestrial integrated network;
• the cache capacity information comprises base station cache capacity information and satellite cache capacity information;
• and
• the link delay information comprises link delay information from the base stations to the base station access users, link delay information from the satellite to the base stations, link delay information from the satellite to the satellite access user, link delay information from the ground station to the satellite, and link delay information from the cloud server to the ground station;
• step (2), determining a content caching problem of a collaboration of the base stations and the satellite for a delay optimization based on differentiated user interests and differentiated access modes, wherein the delay optimization refers to minimizing an average content retrieval delay of all users in the satellite terrestrial integrated network;
• and the step (2) comprises:
• sub-step (2.1), for each region covered by the satellite terrestrial integrated network, calculating, based on a local content popularity distribution in the region, content storage probabilities of a requested content in the base stations, the satellite, the ground station, and the cloud server when the base station access users in the region request any content;
• and
• for each region covered by the satellite terrestrial integrated network, calculating, based on the local content popularity distribution in the region, content storage probabilities of the requested content in the satellite, the ground station, and the cloud server when the satellite access users in the region request any content;
• sub-step (2.2), for each region covered by the satellite terrestrial integrated network, calculating an average content retrieval delay of the base station access users and an average content retrieval delay of the satellite access users, respectively, based on the content storage probabilities and the link delay information;
• sub-step (2.3), performing weighted summation on the average content retrieval delays of all users in all regions within a coverage area of the satellite terrestrial integrated network to obtain a network average content retrieval delay;
• and
• sub-step (2.4), obtaining the content caching problem by taking a content caching strategy of the collaboration of the base stations and the satellite as an optimization variable, minimization of the network average content retrieval delay as an optimization target, and cache capacities of the base stations and the satellite as an optimization limitation condition;
• step (3), solving the content caching problem to obtain the content caching strategy of the collaboration of the base stations and the satellite;
• sub-step (3.1), equivalently converting the average content retrieval delay of the satellite access users in different regions into the average content retrieval delay of all the satellite access users under a global content popularity distribution, in such a manner to reduce a calculation complexity of the average content retrieval delay of the satellite access users;
• sub-step (3.2), reducing a solution space size and reducing a search complexity of the content caching strategy based on solution space analysis;
• sub-step (3.3), converting the content caching problem into a maximization problem of a delay reduction gain, wherein the delay reduction gain refers to a reduction amount of an average content retrieval delay of the users under a current content caching strategy when no content is cached by the base stations and the satellite;
• and
• sub-step (3.4), solving the converted maximization problem of the delay reduction gain to obtain the content caching strategy of the collaboration of the base stations and the satellite;
• and
• step (4), caching, based on the obtained content caching strategy, contents in the base stations and the satellite to provide a content service for the base station access users and the satellite access users in the satellite terrestrial integrated network.