{"bundle_type":"pith_open_graph_bundle","bundle_version":"1.0","pith_number":"pith:2013:7FEGSIYZ4Z5HRDHDBVI3KQLDZR","short_pith_number":"pith:7FEGSIYZ","canonical_record":{"source":{"id":"1309.7712","kind":"arxiv","version":2},"metadata":{"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.IT","submitted_at":"2013-09-30T03:20:39Z","cross_cats_sorted":["math.IT"],"title_canon_sha256":"c954f6f120507a388b4f924f74fc147cc74fab0f79874e4c0f56803134cbd8d8","abstract_canon_sha256":"da88de9487b4fadb3b2b5cba4526180525068ced993147bdc92f2bccb9edbc7f"},"schema_version":"1.0"},"canonical_sha256":"f948692319e67a788ce30d51b54163cc621918fc6f1a48513ff645230dcdb347","source":{"kind":"arxiv","id":"1309.7712","version":2},"source_aliases":[{"alias_kind":"arxiv","alias_value":"1309.7712","created_at":"2026-05-18T01:47:24Z"},{"alias_kind":"arxiv_version","alias_value":"1309.7712v2","created_at":"2026-05-18T01:47:24Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.1309.7712","created_at":"2026-05-18T01:47:24Z"},{"alias_kind":"pith_short_12","alias_value":"7FEGSIYZ4Z5H","created_at":"2026-05-18T12:27:36Z"},{"alias_kind":"pith_short_16","alias_value":"7FEGSIYZ4Z5HRDHD","created_at":"2026-05-18T12:27:36Z"},{"alias_kind":"pith_short_8","alias_value":"7FEGSIYZ","created_at":"2026-05-18T12:27:36Z"}],"events":[{"event_type":"record_created","subject_pith_number":"pith:2013:7FEGSIYZ4Z5HRDHDBVI3KQLDZR","target":"record","payload":{"canonical_record":{"source":{"id":"1309.7712","kind":"arxiv","version":2},"metadata":{"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.IT","submitted_at":"2013-09-30T03:20:39Z","cross_cats_sorted":["math.IT"],"title_canon_sha256":"c954f6f120507a388b4f924f74fc147cc74fab0f79874e4c0f56803134cbd8d8","abstract_canon_sha256":"da88de9487b4fadb3b2b5cba4526180525068ced993147bdc92f2bccb9edbc7f"},"schema_version":"1.0"},"canonical_sha256":"f948692319e67a788ce30d51b54163cc621918fc6f1a48513ff645230dcdb347","receipt":{"kind":"pith_receipt","key_id":"pith-v1-2026-05","algorithm":"ed25519","signed_at":"2026-05-18T01:47:24.686083Z","signature_b64":"kyd/eknIiG4T9DBiGOCNanT0vYqKSxeX1ARASB2LyztIBPGGHSVXtJJWFpS06QQi46WVyVZlibbCNFyD8F7kCw==","signed_message":"canonical_sha256_bytes","builder_version":"pith-number-builder-2026-05-17-v1","receipt_version":"0.3","canonical_sha256":"f948692319e67a788ce30d51b54163cc621918fc6f1a48513ff645230dcdb347","last_reissued_at":"2026-05-18T01:47:24.685395Z","signature_status":"signed_v1","first_computed_at":"2026-05-18T01:47:24.685395Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"source_kind":"arxiv","source_id":"1309.7712","source_version":2,"attestation_state":"computed"},"signer":{"signer_id":"pith.science","signer_type":"pith_registry","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"created_at":"2026-05-18T01:47:24Z","supersedes":[],"prev_event":null,"signature":{"signature_status":"signed_v1","algorithm":"ed25519","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signature_b64":"LN6ZGibDzTfD+DObgm7wm9SRAwJasygGOaiXqVZUHwCSIFs7hmWgy6fKAMjW3Y7EM9IZuhbvo0M8Iujg/Ma9Bg==","signed_message":"open_graph_event_sha256_bytes","signed_at":"2026-06-12T00:24:50.968469Z"},"content_sha256":"c81082c7235c957a6d521889c7a82a65c082f30a5da93870d7f9c64406f1f487","schema_version":"1.0","event_id":"sha256:c81082c7235c957a6d521889c7a82a65c082f30a5da93870d7f9c64406f1f487"},{"event_type":"graph_snapshot","subject_pith_number":"pith:2013:7FEGSIYZ4Z5HRDHDBVI3KQLDZR","target":"graph","payload":{"graph_snapshot":{"paper":{"title":"Downlink Training Techniques for FDD Massive MIMO Systems: Open-Loop and Closed-Loop Training with Memory","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["math.IT"],"primary_cat":"cs.IT","authors_text":"David J. Love, Junil Choi, Patrick Bidigare","submitted_at":"2013-09-30T03:20:39Z","abstract_excerpt":"The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1309.7712","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"},"verdict_id":null},"signer":{"signer_id":"pith.science","signer_type":"pith_registry","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"created_at":"2026-05-18T01:47:24Z","supersedes":[],"prev_event":null,"signature":{"signature_status":"signed_v1","algorithm":"ed25519","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signature_b64":"qWvbyQ3TGQg3X2vIVrxto0DiDPsfSd+1H8RwhXcxvNpS/pR7T9hYMTw9IY3gpQgyXMVSCFQdcPGZU6dT8jknBQ==","signed_message":"open_graph_event_sha256_bytes","signed_at":"2026-06-12T00:24:50.968811Z"},"content_sha256":"313242f97f8da8c105be070184fcfea728896122b20c07464cec092b6dabb519","schema_version":"1.0","event_id":"sha256:313242f97f8da8c105be070184fcfea728896122b20c07464cec092b6dabb519"}],"timestamp_proofs":[],"mirror_hints":[{"mirror_type":"https","name":"Pith Resolver","base_url":"https://pith.science","bundle_url":"https://pith.science/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR/bundle.json","state_url":"https://pith.science/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR/state.json","well_known_bundle_url":"https://pith.science/.well-known/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR/bundle.json","status":"primary"}],"public_keys":[{"key_id":"pith-v1-2026-05","algorithm":"ed25519","format":"raw","public_key_b64":"stVStoiQhXFxp4s2pdzPNoqVNBMojDU/fJ2db5S3CbM=","public_key_hex":"b2d552b68890857171a78b36a5dccf368a953413288c353f7c9d9d6f94b709b3","fingerprint_sha256_b32_first128bits":"RVFV5Z2OI2J3ZUO7ERDEBCYNKS","fingerprint_sha256_hex":"8d4b5ee74e4693bcd1df2446408b0d54","rotates_at":null,"url":"https://pith.science/pith-signing-key.json","notes":"Pith uses this Ed25519 key to sign canonical record SHA-256 digests. Verify with: ed25519_verify(public_key, message=canonical_sha256_bytes, signature=base64decode(signature_b64))."}],"merge_version":"pith-open-graph-merge-v1","built_at":"2026-06-12T00:24:50Z","links":{"resolver":"https://pith.science/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR","bundle":"https://pith.science/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR/bundle.json","state":"https://pith.science/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR/state.json","well_known_bundle":"https://pith.science/.well-known/pith/7FEGSIYZ4Z5HRDHDBVI3KQLDZR/bundle.json"},"state":{"state_type":"pith_open_graph_state","state_version":"1.0","pith_number":"pith:2013:7FEGSIYZ4Z5HRDHDBVI3KQLDZR","merge_version":"pith-open-graph-merge-v1","event_count":2,"valid_event_count":2,"invalid_event_count":0,"equivocation_count":0,"current":{"canonical_record":{"metadata":{"abstract_canon_sha256":"da88de9487b4fadb3b2b5cba4526180525068ced993147bdc92f2bccb9edbc7f","cross_cats_sorted":["math.IT"],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.IT","submitted_at":"2013-09-30T03:20:39Z","title_canon_sha256":"c954f6f120507a388b4f924f74fc147cc74fab0f79874e4c0f56803134cbd8d8"},"schema_version":"1.0","source":{"id":"1309.7712","kind":"arxiv","version":2}},"source_aliases":[{"alias_kind":"arxiv","alias_value":"1309.7712","created_at":"2026-05-18T01:47:24Z"},{"alias_kind":"arxiv_version","alias_value":"1309.7712v2","created_at":"2026-05-18T01:47:24Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.1309.7712","created_at":"2026-05-18T01:47:24Z"},{"alias_kind":"pith_short_12","alias_value":"7FEGSIYZ4Z5H","created_at":"2026-05-18T12:27:36Z"},{"alias_kind":"pith_short_16","alias_value":"7FEGSIYZ4Z5HRDHD","created_at":"2026-05-18T12:27:36Z"},{"alias_kind":"pith_short_8","alias_value":"7FEGSIYZ","created_at":"2026-05-18T12:27:36Z"}],"graph_snapshots":[{"event_id":"sha256:313242f97f8da8c105be070184fcfea728896122b20c07464cec092b6dabb519","target":"graph","created_at":"2026-05-18T01:47:24Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"graph_snapshot":{"author_claims":{"count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","strong_count":0},"builder_version":"pith-number-builder-2026-05-17-v1","claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"paper":{"abstract_excerpt":"The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD ","authors_text":"David J. Love, Junil Choi, Patrick Bidigare","cross_cats":["math.IT"],"headline":"","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.IT","submitted_at":"2013-09-30T03:20:39Z","title":"Downlink Training Techniques for FDD Massive MIMO Systems: Open-Loop and Closed-Loop Training with Memory"},"references":{"count":0,"internal_anchors":0,"resolved_work":0,"sample":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1309.7712","kind":"arxiv","version":2},"verdict":{"created_at":null,"id":null,"model_set":{},"one_line_summary":"","pipeline_version":null,"pith_extraction_headline":"","strongest_claim":"","weakest_assumption":""}},"verdict_id":null}}],"author_attestations":[],"timestamp_anchors":[],"storage_attestations":[],"citation_signatures":[],"replication_records":[],"corrections":[],"mirror_hints":[],"record_created":{"event_id":"sha256:c81082c7235c957a6d521889c7a82a65c082f30a5da93870d7f9c64406f1f487","target":"record","created_at":"2026-05-18T01:47:24Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"attestation_state":"computed","canonical_record":{"metadata":{"abstract_canon_sha256":"da88de9487b4fadb3b2b5cba4526180525068ced993147bdc92f2bccb9edbc7f","cross_cats_sorted":["math.IT"],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.IT","submitted_at":"2013-09-30T03:20:39Z","title_canon_sha256":"c954f6f120507a388b4f924f74fc147cc74fab0f79874e4c0f56803134cbd8d8"},"schema_version":"1.0","source":{"id":"1309.7712","kind":"arxiv","version":2}},"canonical_sha256":"f948692319e67a788ce30d51b54163cc621918fc6f1a48513ff645230dcdb347","receipt":{"algorithm":"ed25519","builder_version":"pith-number-builder-2026-05-17-v1","canonical_sha256":"f948692319e67a788ce30d51b54163cc621918fc6f1a48513ff645230dcdb347","first_computed_at":"2026-05-18T01:47:24.685395Z","key_id":"pith-v1-2026-05","kind":"pith_receipt","last_reissued_at":"2026-05-18T01:47:24.685395Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","receipt_version":"0.3","signature_b64":"kyd/eknIiG4T9DBiGOCNanT0vYqKSxeX1ARASB2LyztIBPGGHSVXtJJWFpS06QQi46WVyVZlibbCNFyD8F7kCw==","signature_status":"signed_v1","signed_at":"2026-05-18T01:47:24.686083Z","signed_message":"canonical_sha256_bytes"},"source_id":"1309.7712","source_kind":"arxiv","source_version":2}}},"equivocations":[],"invalid_events":[],"applied_event_ids":["sha256:c81082c7235c957a6d521889c7a82a65c082f30a5da93870d7f9c64406f1f487","sha256:313242f97f8da8c105be070184fcfea728896122b20c07464cec092b6dabb519"],"state_sha256":"b8d16762c11c051b66aa57b0b7a86d47b1b0c0c0649b1c1fb824f6b0931ccb43"},"bundle_signature":{"signature_status":"signed_v1","algorithm":"ed25519","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signature_b64":"Mhmvv1xUpoY6I1mqCc9BDQ96HOaP1ULAoSerI5ylm0vtH5S0N0abo8ant9RTV8a/q87NRXF3cnmKDMWE4kFDAQ==","signed_message":"bundle_sha256_bytes","signed_at":"2026-06-12T00:24:50.970812Z","bundle_sha256":"8d18a2198ef3bc4bebc41d0600af2bb9c4aa31e058f43003aaf878baa3af97c9"}}